text:
\section{Introduction}

  Transition metal dichalcogenides (TMDs) are for decades attracting significant interest in the scientific community due to their diversity in composition, structure, and electronic phases.
  These include various charge-density-wave states, superconducting phase, Mott, and magnetic insulator states\cite{Wilson1969, Wilson1974, Ogawa1979}.
  Moreover, since the TMDs consist of layers separated by the van der Waals gaps, they offer the possibility of intercalations by various types of atoms and molecules\cite{Friend1977}, further enriching the phase diagrams of these compounds.
  In particular, the intercalation by magnetic ions is interesting since it was shown to produce rather complex magnetic structures in $M_x$TiS$_2$, $M_x$TaS$_2$, $M_x$NbS$_2$, and $M_x$NbSe$_2$ ($M$: 3$d$ transition-metal ions)\cite{Anzenhofer1970, Friend1977, Parkin1980a, Parkin1980b, Parkin1983, Negishi1987, VanderBerg1986}.
  For example 2H-NbS$_2$ is superconducting below 6 K\cite{Maaren1966}.
  If intercalated by Fe, Co and Ni the superconductivity is suppressed in favor of antiferromagnetic ground state, whereas intercalation with V, Mn, or Cr results in the ferromagnetic order\cite{Friend1977, Parkin1980a, Parkin1980b, Parkin1983}.
  Moreover, the chiral magnetic soliton lattice has been recently proposed in case of Cr and  Mn intercalation \cite{Togawa2012,Dai2019}.

  \begin{figure*}[t!]
  \includegraphics[width=\textwidth]{Figure1.pdf}

  \caption{(Color online) (a) Crystal structure of Co$_{1/3}$NbS$_2$.
   (b)The orientations of the photoelectron analyzer and the incident photon beam at the UARPES beamline of the SOLARIS synchrotron. The "horizontal" and "vertical" light polarizations are defined by blue and red arrows.
   The horizontal and vertical polarizations correspond to the $p$- and $s$-polarizations of Ref.~\onlinecite{Himpsel1983}, respectively.
   (c) Atomic subshell photoionization cross-sections for S $3p$, Co 3$d$, and Nb 4$d$, from Ref.~\onlinecite{Yeh1985}}.
  \label{fig1}
\end{figure*}

  The electronic and magnetic properties of TMDs intercalated by 3$d$ transition-metal ions have been traditionally discussed in terms of the rigid-band model.
  Accordingly, portion of the 3$d$ electrons from the intercalated ions are transferred to the rigid transition metal 4$d$ bands, while the remaining portion of 3$d$ electrons, associated with the intercalated ions were considered localized, interacting only weakly with the conduction band and with each other through the Ruderman-Kittel-Kasuya-Yosida (RKKY) and super-exchange mechanisms\cite{Clark1976,Friend1977,Parkin1980a,Parkin1980b}.
  However, this approach was recently questioned in $M_x$NbS$_2$ compounds upon finding non-rigid-band-like changes in electronic structures\cite{Battaglia2007,Sirica2016}, exotic magnetic behaviors\cite{Togawa2012, Dai2019}, and topological semimetal phase\cite{Inoshita2019}.
  It has been also suggested that the usual assumption of the weak coupling between intercalated magnetic moments and itinerant electrons of the host material needs to be abandoned\cite{Sirica2020}.
   Notably, the transport measurements and {\it ab-initio} calculations also indicate the strong hybridization between magnetic sites and metallic layers\cite{Popcevic2019}.
  This strong mixing between itinerant and magnetic degrees of freedom represents the important paradigm shift in magnetically intercalated TMD's.
  Here we delve into it through the first experimental observation of the electronic structure and the Fermi surface of Co$_{1/3}$NbS$_2$ through angle-resolved photoelectron spectroscopy (ARPES).
  The observed spectra in Co$_{1/3}$NbS$_2$ are compared in detail with what is known about the electronic structure of 2H-NbS$_2$.
    The features speaking in favor and against the rigid-band picture are noted one after another.
  The significant departures from the rigid-band picture are explored through theoretical modeling.
  Together, these lead to our main finding that magnetically intercalated TMD's should be regarded as a particular class of strongly correlated electron systems, with the coupling between magnetic and metallic layers essentially responsible for the properties of the material.

\section{Material and methods}
  Co$_{1/3}$NbS$_2$ has the lowest magnetic ordering temperature, $T_{\rm N}\sim26$ K \cite{Friend1977} among the materials of the $M_{1/3}$NbS$_2$ series. The ordering temperature can be additionally decreased by applying  hydrostatic pressure\cite{Barisic2011}.
  The complete suppression of the magnetic order under pressure above 2 GPa has been reported, possibly leading to the Co quantum spin liquid embedded between metallic layers\cite{Barisic2011, Popcevic2019}.
  Small ferromagnetic (FM) canting of Co magnetic moments along the $c$-axis was also suggested recently to occur on the top of the antiferromagnetic ordering below $T_{\rm N}$ \cite{Ghimire2018, Popcevic2019}.
  Large anomalous Hall effect, suggested to originate from complex noncollinear magnetic textures, was recently reported in magnetically ordered state\cite{Ghimire2018}.
  Furthermore, the electrical resistivity along the $c$-axis is significantly lower in Co$_{1/3}$NbS$_2$ than in parent 2H-NbS$_2$, suggesting  that Co atoms act as the conduction links between layers\cite{Popcevic2019}.
  Single crystals of Co$_{1/3}$NbS$_2$ were grown by chemical vapor transport method using iodine as a transport agent\cite{Friend1977}.
   The Co atoms occupy the octahedral voids between NbS$_2$ layers (see Fig.~\ref{fig1} (a)).
   When compared to the 1$\times$1 unit cell of 2H-NbS$_2$, the intercalated compound Co$_{1/3}$NbS$_2$ (space group $P6_322$) forms the $\sqrt{3}\times\sqrt{3}$ supercell rotated by 30$^{\circ}$ \cite{Anzenhofer1970, Parkin1983}.   The corresponding first Brillouin zones, the bigger one for 2H-NbS$_2$ and the threefold smaller for Co$_{1/3}$NbS$_2$,  are shown in Fig.~\ref{fig2}(a).   For brevity, these will be also referred to as "large" and "small" Brillouin zones.
   The grown crystals were characterized by magnetic susceptibility and electrical resistivity measurements.
   Using the Laue diffraction, the crystals were oriented along the high symmetry $\Gamma{\rm M_0}$ and $\Gamma {\rm K_0}$ directions (see Fig.~\ref{fig2} (a) for notation) and glued to Ti flat plates.
  The clean surfaces of the samples were obtained by cleaving $\it{in~situ}$ within the preparation chamber under ultra-high vacuum (better than 3$\times10^{-10}$ mbar), then immediately transferred to the measurement chamber with the base pressure of 8$\times10^{-11}$ mbar.
  The cleaved sample surface was checked before and after performing the ARPES measurement by low energy electron diffraction (LEED).
  The LEED pattern, obtained by using the electrons at the incident energy of 200 eV, clearly showed the periodicity of ($\sqrt{3}\times\sqrt{3}$)$R30^{\circ}$ reciprocal lattice.

  The experiment was performed at the UARPES beamline of the SOLARIS synchrotron, using the photons in the 34-79 eV energy range.
  Within this energy range, the photoionization cross-section of Niobium 4d orbitals diminishes by two orders of magnitude, whereas the photoionization cross-sections of Sulphur 3p and Cobalt 3d orbitals stay unchanged, as shown in the Fig.~\ref{fig1}(c).
  This we used to separate the electronic band features originating from S and Co orbitals from those arising from Nb orbitals.
   Photoelectrons were collected using a hemispherical analyzer DA30 (VG Scienta) and a multi-channel plate coupled to a CCD detector.
   The overall energy resolution was estimated to be 20 meV from the Au Fermi edge fitting.

\begin{figure*}[t!]
  \includegraphics[width=\textwidth]{Figure2.pdf}
  \caption{(Color online). (a) Bulk Brillouin zone of 2H-NbS$_2$ (top) and the surface Brillouin zones of 2H-NbS$_2$ and Co$_{1/3}$NbS$_2$ (bottom), shown in black and blue lines, respectively.  These will also be referred to as "large" and "small" Brillouin zones for brevity Energy distribution curves (EDCs) along (b) $\Gamma {\rm M_0}$ and (c) $\Gamma {\rm K_0}$ lines in the $k$-space. The ARPES intensity plots for Co$_{1/3}$NbS$_2$ measured along (d) $\Gamma {\rm M_0}$ and (e) $\Gamma {\rm K_0}$ directions using the $h\nu=40$ eV photons, and horizontal polarization.
In order to cover an extended momentum range, three ARPES images collected $\pm15^{\circ}$-frame are stitched.
  The vertical dashed lines represent the boundaries of the Co$_{1/3}$NbS$_2$ first Brillouin zone.
  The lines composed of blue and yellow dots represent the energy bands calculated for 2H-NbS$_2$, with the unit cell adjusted to Co$_{1/3}$NbS$_2$, and additional $4/3$ electrons per unit cell (see text).
  The blue and yellows dots stand for states predominantly composed of Nb- and S-derived orbitals, respectively.
  The calculated bands are subsequently shifted by 0.1 eV with respect to the Fermi level in the direction that increases the conduction band filling.}
  \label{fig2}
  \end{figure*}

  The linearly polarized light was used in the experiment.
  The experimental setup and two polarization directions used in our measurements are schematically shown in Fig.~\ref{fig1}(b).
   The polarization is called "horizontal" when the electric field vector of the incident light is parallel to the "incident plane" (the light blue plane in Fig.~\ref{fig1} (b)) defined by the light propagation vector and the normal to the sample surface.
   The polarization is called "vertical" when the electric field vector of the incident light is perpendicular to the incident plane and parallel to the "emission plane" (the light orange plane in Fig.~\ref{fig1} (b) defined by the direction of the analyzer slit.
   The total intensity of each ARPES spectrum, extending over a measured span of electronic momenta and the binding energy between 0 and 4 eV, is subsequently normalized to the same value.

  The band structure for 2H-NbS$_2$ was calculated using the Quantum ESPRESSO Density Functional Theory (DFT) package\cite{Giannozzi2009, Giannozzi2017}.
  The kinetic energy cutoff of 70-80 Ry for wavefunctions and the kinetic energy cutoff of 500-600 Ry for the charge density and potentials was used.
  The ultrasoft pseudopotentials are from pslibrary\cite{DalCorso2014} based on Perdew-Burke-Ernzerhof exchange-correlation functional\cite{Perdew1996}.
   The Fermi-energy discontinuity is smeared as proposed by Marzari-Vanderbilt\cite{Marzari1999} with broadening of 0.005-0.01 Ry.
   Several different DFT calculations were conducted using the DFT-optimized crystal structure unless otherwise stated.
   For the pristine NbS$_2$, the DFT optimized crystal lattice parameters are found to be a$_0$ = 3.349 \AA \phantom{ }and c$_0$ = 13.495 \AA, with the vertical position of Sulphur atom at z = 0.133.
   The DFT optimized crystal lattice parameters for antiferromagnetically ordered Co$_{1/3}$NbS$_2$, with orthorhombic unit cell, are a$_1$ = 5.792 \AA, b$_1$ = 10.032 \AA (= a$_1\sqrt{3})$ and  c$_1$ = 12.199 \AA \cite{Popcevic2019}.
   The crystal parameters for calculation of NbS$_2$ with 2/3 extra electrons per Nb atom are inferred from DFT optimized antiferromagnetically ordered Co$_{1/3}$NbS$_2$ crystal parameters, a$_2$ =  3.344 \AA (= a$_1/\sqrt{3})$ and c$_2$ = 12.199  \AA (= c$_1$) with vertical Sulphur position z = 0.123\cite{Popcevic2019}.
     The k-point mesh of $20\times20\times8$ in the Brillouin zone was used with no shift.

\section{Experimental results}

\subsection{Scans along cuts in k-space}

  Fig.~\ref{fig2} shows the ARPES spectra of Co$_{1/3}$NbS$_2$ collected along $\Gamma {\rm M_0}$ and $\Gamma {\rm K_0}$ directions of the Brillouin zone  of 2H-NbS$_2$.
  They were measured at photon energy $h\nu=$ 40 eV using the horizontal photon polarization.
   Energy distribution curves (EDCs) along these directions are also shown.
  The zero in binding energy ($E_B$) corresponds to the Fermi level ($E_{\rm F}$).
   The blue dashed lines in panels (d) and (e), and full blue lines in panels (b) and (c) correspond to the Brillouin zone boundaries of Co$_{1/3}$NbS$_2$.
   The spectra on panels (b) and (d) (along $\Gamma$K$_0$ direction) are recorded at 78 K, while the spectra at panels (c) and (e) along $\Gamma$M$_0$ direction are measured at 10 K.
  We point out that $k$-axes essentially specify the $(k_x, k_y)$ coordinates of the initial electron state, and we use the surface Brillouin zone labels to emphasize that. The corresponding labels without bars designate the points at $k_z=0$ in the bulk Brillouin zone, whereas in reality $k_z$ can be finite. We will return to this point in Sec.~\ref{sec:discussion}.
    We also compared the ARPES spectra measured below and above the magnetic ordering temperature $T_{\rm N}$, taken along the same direction.
  We have not observed any significant differences between these spectra within the experimental resolution, except for the thermal broadening around the Fermi level.
   The details are provided in Ref. \onlinecite{SIref}.
   Some differences in data quality observed along different directions in spectra presented in Fig.~\ref{fig2} should be primarily attributed to different crystal qualities of samples used for scans along different directions\cite{SIref}.

The solid circles in panels (d) and (e) in Fig.~\ref{fig2}  represent the electronic band dispersions obtained from the DFT calculation for the parent compound, as detailed in Appendix B.
   The EDCs show pronounced dispersive features in the energy windows of $E_B$ = 0-1 eV and 2-4 eV.
   Two bands can be discerned from the spectra in the energy range between zero and 1 eV binding energy (more so along the $\Gamma$K$_0$ direction where the data quality is somewhat higher).
   In the region between 2 and 4 eV binding energy, the signal is more smeared, and individual bands are hard to discern without using the calculated band structure as a reference.

  Fig.~\ref{nfig3} shows the ARPES intensity plots measured at $h\nu$ = 62 eV, using horizontal and vertical polarization setups.
  The intensity distribution of S 3$p$-derived bands in the $E_B$ = 2-4 eV region is more homogenous for the horizontal than vertical polarization.
  A similar difference regarding polarizations can be seen in spectra taken using 40 eV photons\cite{SIref}.
The comparison of spectra in Fig.~\ref{nfig3}(a) and Fig.~\ref{fig2}(e) shows that more bands can be observed at higher photon energy, especially in the $E_B$ = 2-4 eV region.

  \begin{figure}[t]
  \includegraphics[width=\columnwidth]{Figure3.pdf}
  \caption{(Color online). ARPES intensity plots of Co$_{1/3}$NbS$_2$ along the $\Gamma {\rm K_0}$ direction for
   (a) horizontal and (b) vertical photon polarization. The spectra are measured with $h\nu$ = 62 eV at 10 K.
    The dashed lines in light-blue mark the M high symmetry point at the boundary of the first Brillouin zone of Co$_{1/3}$NbS$_2$. }
  \label{nfig3}
  \end{figure}

  \begin{figure*}[t!]
  \includegraphics[width=\textwidth]{Figure4.pdf}
  \caption{(Color online). The ARPES intensity plots along $\Gamma{\rm K_0}$ direction measured with different energy of the photons used in the experiment.
  All ARPES images are measured using horizontal polarization and plotted in the same intensity scale.
  Blue dashed lines correspond to the boundaries of first Brillouin zone of Co$_{1/3}$NbS$_2$. The green vertical lines in the first panel denote the cuts taken in the spectrum leading to 40 eV curves in Figs.~\ref{nfig5}(a) and (b).}
  \label{nfig4}
  \end{figure*}

  This can be further appreciated by following the panels in Fig.~\ref{nfig4}, where we show ARPES intensity plots of spectra measured at ten photon energies, ranging from $h\nu$ = 40 to 76 eV.
  These spectra were normalized separately for each panel and plotted using the same intensity scale.
The most notable feature of Fig.~\ref{nfig4} is the shift in intensity from lower to higher binding energy upon rising the photon energy.
  The exception may be spotted with the signal at 3 eV binding energy at $\Gamma$ point, which loses the intensity upon increasing the photon energy.
  The non-monotonous intensity dependence on photon energy is also seen for the signal around 1.5 eV binding energy.
  As announced, these features will be discussed in more detail in the next section.

\subsection {The constant energy scans}

  \begin{figure}[t!]
  \includegraphics[width=\columnwidth]{Figure5.pdf}
  \caption{(Color online) Constant energy cuts at the Fermi level, measured at 10 K using  $h\nu$ = 40 eV photons, in (a) horizontal (a) and  (b) vertical polarization setups. The panels (c) and (d) show the data obtained using $h\nu$ = 62 eV photons, respectively in horizontal and vertical polarization.
  The large black hexagon and the small hexagons shown in light-blue dashed line represent the first Brillouin zones of NbS$_2$  and Co$_{1/3}$NbS$_2$, respectively. }
  \label{figk1}
  \end{figure}

  Fig.~\ref{figk1} shows the signal at the Fermi level of Co$_{1/3}$NbS$_2$ measured at photon energies of 40 and 62 eV using horizontal and vertical polarizations.
   Two concentric Fermi surface sections are observed around K$_0$ point, while only one circular Fermi surface section is present around the $\Gamma$ point.
  The additional set of signals is found around the boundary of first Brillouin zone of Co$_{1/3}$NbS$_2$, or  the ($\sqrt{3}\times\sqrt{3}$)$R30^{\circ}$ superlattice of 2H-NbS$_2$.
  The signals are visible in both photon polarizations and best seen in scans made by using 62 eV energy photons.
   We call this set of signals the "$\beta$"-band, following Ref. \onlinecite{Sirica2016} where a somewhat similar feature was first observed in the sister compound Cr$_{1/3}$NbS$_2$ and termed the "$beta$-feature".
    Contrary to Cr$_{1/3}$NbS$_2$ spectra, in Co$_{1/3}$NbS$_2$ we observe the "$\beta$"-band in constant energy scans as a much more structured signal, spreading throughout the boundary of the first Brillouin zone of Co$_{1/3}$NbS$_2$.
  In the 40 eV photon energy scans (Fig.~\ref{figk1} (a) and (b)), the $\beta$-band can probably be described as another large ring around $\Gamma$-point, concentric to the antibonding Nb $d$ band Fermi surface.
  This is how the $\beta$-feature was primarily described in Cr$_{1/3}$NbS$_2$ \cite{Sirica2020}.
  The scans at 62 eV photon energy (Figs.~\ref{figk1} (c) and (d)) provide better images of the $\beta$-band, as the "circle" of six triangularly shaped or dewdrop-like pockets surrounding the K-points at the boundary of the small Brillouin zone.

  \begin{figure}[t!]
  \includegraphics[width=0.5\textwidth]{Figure6.pdf}
  \caption{(Color online). Constant energy cuts at (a) $E_{\rm F}$, (b) 20 meV below $E_{\rm F}$ and (c) 40 meV below the Fermi energy of Co$_{1/3}$NbS$_2$, measured at 10 K with $h\nu$ = 62 eV in horizontal polarization.
  The large black hexagons and the small hexagon shown in light-blue dashed line represent the first Brillouin zones of NbS$_2$  and Co$_{1/3}$NbS$_2$, respectively.
     (d) Left half of the Fermi surface shown on panel (a) is presented with ARPES spectra along $\Gamma$ - M$_0$ direction down to 0.3 eV binding energy.}
  \label{figk2}
  \end{figure}
  One can follow these pockets to energies below the Fermi level, assisted by constant energy scans shown in Fig.~\ref{figk2}.
  The panels (a), (c), and (d) in Fig.~\ref{figk2} indicate the collapse of the pockets towards K-points at higher binding energies, identifying the $\beta$-band as a collection of shallow electron pockets, of few tens of meV in depth.
   On a more quantitative side, the size of each pocket can be estimated to around 2 \%/ of the large Brillouin zone, and their depth to $(40 \pm 10)$ meV.
  Within simple parabolic approximation  $\mathcal{E}_\beta=\hbar^2 ( k_\beta)^2/2m_\beta^*$, with  $\mathcal{E}_\beta$ and $k_\beta$ denoting the depth and the radius of one pocket, this yields the effective mass $m_\beta^*=(2.4 \pm 0.6) m_e$ for these pockets, roughly two times bigger than the effective mass $m_0^*$ appropriate to conducting bands of 2H-NbS$_2$. The latter is  determined from the Fermi velocity in 2H-NbS$_2$ in the usual way,  $m_0^*=\hbar k_F/v_F$, with $v_F$ being read from the slope of the electronic dispersion, and $k_F$ being the characteristic wave vector (radius) of the Fermi surface section. Of course, while two approaches to read the effective mass from the electronic dispersion are equivalent for quadratic band dispersions, the former is easier to apply for shallow pockets.

  It should be mentioned that in the sister compound Cr$_{1/3}$NbS$_2$ the "$\beta$-feature" undergoes splitting into two signals below the helical/ferromagnetic ordering temperature.
   This was argued in favor of the Cr nature of the "$\beta$-feature".
   The resonant photo-emission (ResPES) study suggests the same\cite{ Sirica2016,Sirica2020}.
   In Co$_{1/3}$NbS$_2$, we do not observe any significant temperature dependence of the $\beta$-band\cite{SIref}.

\section{Discussion of experimental results} \label{sec:discussion}

\subsection{Scans along cuts in k-space}

   The surface sensitivity of ARPES often casts doubt on the relevance of the observed band structure to the bulk electronic structure.
   For intercalated quasi-two-dimensional TMDs, a cleavage is expected to happen at a layer defined by the intercalated ions, where the binding is weaker than within host material TMD layers.
   By symmetry, an ideal cleavage is expected to divide the intercalate (Co) atoms equally between the two cleaved surfaces, thus leaving disordered Co at the very surface.
   The relevance of this surface effect to the interpretation of the measured spectra as the genuine electronic structure of bulk material was assessed for the sister compound Cr$_{1/3}$NbS$_2$ \cite{Sirica2016}.
   Two types of termination layers were reported, observed by scanning tunneling microscopy on $in~situ$ cleaved Cr$_{1/3}$NbS$_2$.
   The first was the termination layer with disordered Cr atoms, which was connected to the observation of the non-dispersive bands in ARPES spectra\cite{Sirica2016}.
   The second was the termination layer with ordered S atoms, where, according to Sirica {\it et~al.}\cite{Sirica2016},  the band dispersions and Fermi momentum obtained by low energy ARPES were not significantly modified with respect to those of bulk Cr$_{1/3}$NbS$_2$\cite{Sirica2016}.
    In Co$_{1/3}$NbS$_2$, we do not observe non-dispersive bands in the measured energy range, suggesting no significant influence of Co disorder on our spectra.

     In ARPES spectra presented in Figs. \ref{fig2}, \ref{nfig3} and \ref{nfig4}, no clear evidence of the band folding or discontinuations (gaps) were observed at the boundary of the first Brillouin zone of Co$_{1/3}$NbS$_2$, or the ($\sqrt{3}\times\sqrt{3}$)$R30^{\circ}$ superstructure of 2H-NbS$_2$ imposed by intercalation.
   This is in accordance with previous reports in (Mn, Cr)$_{1/3}$NbS$_2$ \cite{Battaglia2007, Sirica2016}.
  This finding will also be addressed in further sections, but for the moment, it may be regarded as the additional reason to start our discussion of the measured spectra by comparing them to electronic bands calculated for the parent material 2H-NbS$_2$.
  Of course, the first reason for taking this approach is the decades-old dominance of the rigid band picture in the field of magnetically intercalated TMD's.

  The Nb $4d$ states play a major role in the metallic properties of 2H-NbS$_2$.
  In 2H-NbS$_2$ the Nb atom is surrounded by six S atoms, forming the NbS$_6$ prism with the $D_{3h}$ symmetry (see  the Fig.~\ref{fig2} (a)), and leading to Nb $4d$ orbitals split into $a_1'$ ($d_{z^2}$), $e'$ ($d_{xz, yz}$), and $e''$ ($d_{x^2-y^2, xy}$) states.
     According to electronic structure calculation, the bands crossing the Fermi level are primarily composed of Nb $4d_{z^2}$ orbitals, and, to a smaller extent, of S $p_z$ orbitals\cite{Popcevic2019}.
    With two Nb atoms per  2H-NbS$_2$ unit cell, two conduction bands emerge from the calculation, as shown in Fig.~\ref{fig2} (e).
      These two bands can also be discerned from the experimental spectra in Fig.~\ref{fig2} (e), covering most of the energy range between zero and 1 eV binding energy,
    The lower band corresponds to the bonding, whereas the upper band corresponds to the antibonding combination of Nb $4d_{z^2}$ orbitals of the two Nb layers in the unit cell.
   The one noticeable difference between the experiment and the calculated bands shows in the central part of the figure: As the $\Gamma$ point is being approached, the splitting between observed bands gets much more prominent than for calculated bands, with the lower band reaching the $\Gamma$ point around 0.3 eV below the Fermi level, whereas the calculated Nb bonding band approaches and crosses the Fermi level before reaching the $\Gamma$ point.
   We will return to this point in the second part of this section, where the deviations from the rigid band picture are addressed separately.
  Further on, the dispersions of the bands measured in the energy window of $E_B$ = 2-4 eV, presented in Figs. \ref{fig2} (a) and (b), agree rather well with the bands calculated for 2H-NbS$_2$.
  According to our calculations, these bands are mostly built from Sulphur orbitals, with a small contribution from Nb orbitals appearing around $\Gamma$-point at $E_B\sim$ 3 eV, as indicated in the Figs. \ref{fig2} (d) and (e).

\subsection {Effect of photon polarization and photon energy on ARPES spectra}

  Several factors influence the intensity variation within a single ARPES spectrum and the differences between spectra taken at different setups.
  Those differences are usually attributed to the dependence of the transition matrix element on photon energy, light polarization, symmetry of the underlying electronic wavefunctions, as well as the geometry of the experimental setup\cite{Moser2017}.
   The influence of light polarization on ARPES intensity  in Co$_{1/3}$NbS$_2$ is exemplified through Fig.~\ref{nfig3}.
   The spectra recorded using different photon polarizations are usually used to analyze the orbital content of the electronic bands\cite{Cao2013, Sirica2016}.
   For this, it is advantageous to align the emission plane of the experimental setup to the mirror plane of the crystal.
  Unfortunately, this condition cannot be fulfilled in our case, as the intercalated compound has no mirror symmetry planes.

   The influence of variation in photon energy on ARPES spectra is shown in Fig.~\ref{nfig4}.
     It primarily manifests through the shift in intensity from lower to higher binding energy upon rising the photon energy.
   This shift is in accordance with Fig.~\ref{fig1}(c) and our expectations regarding the atomic character of different bands, encoded through colors of the calculated curves in Figs.~\ref{fig2}(d) and (e), with Nb orbitals contributing mainly to bands up to 1 eV binding energy, and Sulphur orbitals dominating the bands in the remaining part of the spectrum.

  In principle, the variation of photon energy can also offer information on band dispersion in the direction perpendicular to the surface, i.e., the $k_z$ dispersion\cite{Damascelli2004}.
  Of course, in TMDs, which are usually described as quasi-two-dimensional systems, this dispersion is expected to be weak compared to band dispersion in the direction parallel to layers.
  On the other hand, the band dispersion in the direction perpendicular to layers may be particularly interesting in intercalated materials as the intercalation is expected to change the coupling between layers.
  Indeed, the Co-intercalation in 2H-NbS$_2$ was found to reduce the electrical resistivity in the direction perpendicular to layers by approximately two times and very much reduce the anisotropy of electrical resistivity, although mainly through increasing the resistivity in the direction parallel to layers\cite{Popcevic2019}.
  The DFT calculations in Co$_{1/3}$NbS$_2$ predict the bonding Nb $d_{z^2}$ band crossing the Fermi level along the $k_x=0$, $k_y=0$ axis with considerable $k_z$ dispersion\cite{Popcevic2019}.
  The same calculations also predict the $k_z$ dispersion for the topmost Sulphur band as the most pronounced\cite{Popcevic2019, SIref}.
  One can expect these dispersion effects to be observable  in Fig.~\ref{nfig4}, as different photon energies should reflect initial electronic states at different $k_z$'s, for any fixed values of $k_x$ and $k_y$.
  The momentum along the $z$ direction may be calculated using the expression\cite{Damascelli2004}:
  \begin{equation} \label{eq:kz}
  k_z=\sqrt{\frac{2m}{\hbar^2}(E_k{\rm cos}^2\theta+V_0)}.
  \end{equation}
  Here $E_k$ is the kinetic energy of photoelectrons at the detector, $\theta$ is the angle between the surface normal and photoelectron wave vector, $m$ is the free electron mass, and V$_0$ is the inner potential.
  The value of V$_0$ is generally determined experimentally, with the $V_0$ = 14 eV being recently proposed for the sister compound Cr$_{1/3}$NbS$_2$\cite{Sirica2016}.
  With $V_0$ of this magnitude, and the span in photon energy covered by Fig.~\ref{nfig4}, one expects to scan over the $k_z$ range exceeding the total height of $2\pi/c$ of the first Brillouin zone.
  However, the changes in band position foreseen by bands structure calculation cannot be discerned in Fig.~\ref{nfig4}.
  There are several possible explanations.
  On the one hand, it is possible that the DFT calculation very much overestimates the interlayer-coherence upon assuming the frozen magnetic order in the material where the interlayer coupling is primarily coming from magnetic ions.
  The Co spin fluctuations, presumably present down to very low temperatures in Co$_{1/3}$NbS$_2$, provide an excellent mechanism to destruct the interlayer coherence.
  However, the temperature dependence of resistivity in direction perpendicular to layers does not necessarily suggest that\cite{Popcevic2019}.
  On the other hand, there are works discussing the low $k_z$ sensitivity in ARPES performed at photon energies below one hundred eVs\cite{Strocov2003}, related to rather short "escape length", which measures the depth from which the electron can be extracted without being scattered. In our case, this depth is estimated by using the Tanuma-Powell-Penn (TPP-2M) formula\cite{Tanuma1994} to $4.5$ \AA, less than half a value of the c-axis lattice constant.
  Finally, the sample quality has been seen to influence the quality of the signal, where weaker signals originating from dispersive bands are likely to suffer the most.

\subsection {Rigid band picture and beyond}

  Another view at data underlying Fig.~\ref{nfig4} can be acquired through energy distribution curves (EDC) presented in Fig.~\ref{nfig5}.
  Extracted from the same data set, the EDCs provide a real "features inventory".
  In panel  Fig.~\ref{nfig5} (a), we focus on signals at the $\Gamma$ point, whereas panel (b)  helps to follow these features away from the $\Gamma$ point.  Both figures include 14 spectra taken at different photon energies.
  We inspect these figures to determine to which degree the ARPES spectra conform the picture of rigidly shifted NbS${_2}$ bands.
   Five features can be discerned in most curves in Fig.~\ref{nfig5} (a), labeled by $a$ through $e$, starting from the one closest to the Fermi energy.

  \begin{figure}[!ht]
  \includegraphics[width=\columnwidth]{Figure7.pdf}
  \caption{(Color online) Energy distribution curves (EDCs) at two position in $k$-space, marked by
  (a) Energy distribution curves (EDCs) at $\Gamma$ point measured for various energies of incident photons.
   The main spectral features are indicated by vertical bars and labels below the bottommost curve.
   (b) EDCs at k$_x$ = 0.295 \AA$^{-1}$. This point in k-space is marked by the green line and $b$ label on the first panel of Fig.~\ref{nfig4}. }
  \label{nfig5}
  \end{figure}

   We start our inspection from feature $e$, found at $E_B$ = 3 eV in panel (a).
  The intensity of this signal decreases with increasing photon energy.
  This behavior points to the Niobium character of the signal, as expected from the DFT calculations shown in Figs.~\ref{fig2} (d) and (e), where the blue dotted curves indicate states with prevailing contribution from Niobium.
   The DFT calculations predict several bands crossing the $\Gamma$ point at this energy, with one group of bands curved upward and another group of bands curved downward around the $\Gamma$ point.
   In Fig.~\ref{nfig5}(b) we can identify the upward curved bands while downward curved ones are not readily observable further away from the $\Gamma$ point.

     The feature $d$, located at $E_B$ = 2 eV, gets enhanced at higher photon energies, indicating its dominantly Sulphur character.
  Again, this is consistent with the DFT calculations predicting four dominantly Sulphur bands merging at $\Gamma$ at $E_B$ = 2 eV.
   These bands, all showing maxima at or around $\Gamma$  in Fig.~\ref{fig2}, cannot be individually resolved from measured spectra.

  Although the signal is less abundant in the $E_B\approx$ 1-2 eV energy range, at least two bands can be discerned in this range from most of the panels in Fig.~\ref{nfig4}.
   The first one, labeled $c$ in Fig.~\ref{nfig5}, is visible mostly around $\Gamma$ point at $E_B$ = 1.3 eV.
   The second one, labeled $b$ in Fig.~\ref{nfig5}, can be observed at $E_B$ = 0.8 eV.
  Only one band in this energy range appears in 2H-NbS$_2$ band structure calculations.
  This is the highest lying Sulphur $p$-band, whose position and the energy span appears to be particularly sensitive to changes in the c-axis lattice constant, as shown in Appendix ~B.
  The calculations also predict the pronounced $k_z$ dispersion for this band, which we cannot confirm from the experiment.
  The deviations from simple rigid band picture become more pronounced upon addressing the feature $a$, appearing at $\Gamma$ point at 0.3 eV below the Fermi energy, and persisting in most of the EDCs in Fig.~\ref{nfig5} (a).
  This feature does not appear in the DFT spectra and, as announced earlier, can be identified as the Nb 4$d$ bonding band.
  We have also announced that the DFT calculated bands for pristine 2H-NbS$_2$, (Appendix, Fig.~\ref{figA2}(a)), rigidity shifted to account for the charge transfer from Co ions, do not predict the bonding Nb 4$d$ band getting below Fermi level at $\Gamma$ point.
  The same applies for DFT calculations for 2H-NbS$_2$ with two extra electrons per three NbS$_2$ units, simulating the charge transfer from Co atoms, added to NbS$_2$ layers from the outset  ( Figs. \ref{fig2}(d) and (e) and Appendix Figs.~\ref{figA2}(b)).
   This indicates that Co intercalation goes well beyond the charge transfer, strongly increasing the interlayer hybridization and the splitting between Nb $4d$ bands around $\Gamma$ point, to the level of pushing one conduction band maxima much below the Fermi level.
  The same was observed in ARPES spectra in Cr$_{1/3}$NbS$_2$ \cite{Sirica2016}.
  This is also the robust feature of DFT results in Co$_{1/3}$NbS$_2$,  as discussed in Ref.~\onlinecite{Popcevic2019},  and expanded upon in the next section.
  The effects of the extra band splitting diminish upon moving away from the zone center, leading to the "non-uniform doping" across the Fermi surface, as termed in Ref.~\onlinecite{Battaglia2007} for Mn$_{1/3}$NbS$_2$ and Ni$_{1/3}$NbS$_2$.
  Therefore, the pronounced non-uniform deformation of conduction bands appears to be the general consequence of intercalation of 2H-NbS$_2$ by transition metal ions.

\subsection{The signal at the Fermi level}

  For the Fermi level, the rigid band picture foretells two hole-like pockets appearing around $\Gamma$ point, as well as around K$_0$ point.
   The only expected difference from the Fermi surfaces measured in pristine 2H-NbS$_2$\cite{Youbi2020} would be the reduction in the size of those pockets caused by the electron transfer from Co into NbS$_2$ layers.
   In fact, this kind of reduction in size was already reported for sister materials Mn$_{1/3}$NbS$_2$ and Ni $_{1/3}$NbS$_2$  in Ref. \onlinecite{Battaglia2007}.
   Given the submergence of bonding Nb 4$d$ band maximum below the Fermi level, one further expects to lose one pocket in the central part of the Brillouin zone, leaving only one circular hole pocket around  $\Gamma$, related to the antibonding band.
    This circular Fermi surface around $\Gamma$ is what we observe for all photon energies, along with the pockets around $K_0$, as pictured in   Fig.~\ref{figk1}.

  However, Figs.~\ref{figk1} and \ref{figk2} also bring in the biggest difference between electronic structures of Co$_{1/3}$NbS$_2$ and the parent compound 2H-NbS$_2$.
  Entirely unforeseen by the latter, the "$\beta$-band" appears in the vicinity of the Fermi level, in the region too narrow in energy to be easily spotted in Fig.~\ref{nfig4} and in other spectra that present data in the entire binding energy range covered by the experiment.
  In the $k$-space, the $\beta$-band shows as the necklace of  shallow and wide electron pockets positioned around K-points of the small Brillouin zone imposed by intercalation, weakly overlapping.
Not only that the 2H-NbS$_2$ rigid-band picture cannot account for the $\beta$-band, but the same applies to any conceivable "deformation" of the 2H-NbS$_2$ bands.
   As mentioned in the previous section, a somewhat similar $\beta$-feature was first observed recently in sister compound Cr$_{1/3}$NbS$_2$.
   Despite this feature receiving much attention in Ref. \onlinecite{Sirica2020}, and being convincingly attributed to Cr orbitals, its origin remains elusive.
  In Co$_{1/3}$NbS$_2$ we observe the feature much more clearly, fully developed.
  The fact that the $\beta$-band gets increasingly pronounced at higher photon energies corroborates its Cobalt character.
  This goes well in hand with the Cr-origin of the $\beta$-feature in Cr$_{1/3}$NbS$_2$ concluded upon by other means.
  The possibility of the $\beta$-band/feature coming from magnetic atoms remaining on the surface upon cleavage seems very unlikely.
  The structured ARPES signal, well away from the $\Gamma$ point, would demand the surface reconstruction neatly ordering these atoms, which was not seen in Cr$_{1/3}$NbS$_2$.
  It should be further noted that no explanations of the $\beta$-feature\cite{Sirica2016,Sirica2020} or the $\beta$-band can be found in published {\it ab initio} electronic structure calculations in magnetically intercalated TMDs, and  in Co$_{1/3}$NbS$_2$ in particular\cite{Nakayama2006, Mankovsky2016,Inoshita2019,Popcevic2019,Ghimire2018}.

\section{Modeling the electronic structure of Co$_{1/3}$NbS$_2$ }

\subsection{Unfolded DFT spectra}

  As stated towards the end of the previous section, no explanation of the $\beta$-band can be found in published {\it ab initio} electronic structure calculations in Co$_{1/3}$NbS$_2$\cite{Nakayama2006, Mankovsky2016, Inoshita2019, Popcevic2019}.
   Still, these calculations contain several features worth noticing, and the comparison between such a DFT calculation to our ARPES spectra seems worth doing.
  Subsequently, we discuss ways and mechanisms beyond such DFT calculations that may be responsible for the observed $\beta$-band.

  To start with, the spin 3/2 magnetic state of Co convincingly shapes several experimental properties of Co$_{1/3}$NbS$_2$, and in particular the Currie-Wiess behavior of the magnetic susceptibility, in a wide temperature range.
  DFT may catch this prominent property of the electronic system only by addressing the magnetically ordered state and spin-polarized calculations.
  Alternatively, the electronic states emerging from the calculation are characterized by the same density of spin-up and spin-down electrons at all Co sites.
  The DFT+U approach\cite{Martin2004, Tolba2018}, which includes the Coulomb Hubbard correction $U$ to local interactions, turns helpful in better addressing the electronic correlations on Co atom and in reproducing the magnetic moment measured experimentally.
  Our self-consistent determination of $U$ within the DFT+U approach yields $U\approx 5$ eV at Co atom.
This value of $U$ was also used in several previous studies in compounds with Co atoms\cite{Juhin2010,Chen2011,Mann2016}, and the value used in our {\it ab initio} calculations in Co$_{1/3}$NbS$_2$ in  Ref. ~\onlinecite{Popcevic2019}.
  The latter is the calculation that we will be using to compare with our experimental data.

   The calculation was performed for the particular antiferromagnetically ordered state termed the hexagonal order of the first kind (HOFK), determined for Co$_{1/3}$NbS$_2$ by neutron scattering a long time ago\cite{Parkin1983}.
  The first Brillouin zone appropriate for this state is six-fold smaller than the first Brillouin zone of 2H-NbS$_2$ and significantly smaller than the $k$-vector range covered by experimental scans.
  For this reason, as well as to account for the signal variation in $k$-space introduced by  "super-structuring" induced by intercalation, the "unfolding" procedure is applied to the DFT-calculated spectra before comparing them to our ARPES results.
    As usual, the unfolding determines the spectral weights in the extended $k$-space range based on the calculated wavefunctions.

    We confine our comparison to the energy range of approximately 1 eV below the Fermi level, dominantly covered by bands originating from Nb and Co orbitals.
  We choose to make the unfolding starting from the faithful tight-binding (TB) parametrization of the DFT-calculated bands, obtained by using the Wannier90 code\cite{Wannier902014, SIref}.
  The unfolding procedure essentially follows the one outlined in Ref. \onlinecite{Wu2017}, with the in-house code developed for the occasion.
  The choice of using the effective tight-binding approach has some advantages.
  First, the TB parameters have direct physical significance, especially when only a few are required to shape the bands rather well.
  Second, the bands calculated for 2H-NbS$_2$ and Co$_{1/3}$NbS$_2$  can be easily compared through these parameters.
  Finally, the differences between calculated and measured spectra can be explored by adjusting these parameters, possibly leading to improved electronic modeling of the material.

  \begin{figure}[t!]
  \includegraphics[width=0.45\textwidth]{Figure8.pdf}
  \caption{(Color online). The electronic spectra calculated for Co$_{1/3}$NbS$_2$ (see Ref. \onlinecite{Popcevic2019}) in the particular antiferromagnetically ordered state, termed  "hexagonal order of the first kind" (HOFK).  The electronic bands are shown unfolded along M$_0$$\Gamma$K$_0$ line of Brillouin zone  of 2H-NbS$_2$, properly weighted  by their contributions at each k-point.
  The contributions along inequivalent directions in the HOFK state are suitably taken into account. The inset shows the spectral weight at the Fermi energy, with the boundary of the first Brillouin zone of the of Co$_{1/3}$NbS$_2$ shown in a white dotted line.
  The color bar indicates the intensity scale.}
  \label{figEM-A}
  \end{figure}

  The unfolded spectra are shown in Fig.~\ref{figEM-A}.
  The overall spectral distribution broadly follows the spectral shape of the 2H-NbS$_2$ conduction bands.
  Along with commonalities, some differences are readily spotted.
  The most apparent difference emerges through the bonding Nb  $d$-band found submerged below the Fermi level near the $\Gamma$ point.
  At this point, the {\it ab initio} electronic structure calculations in Co$_{1/3}$NbS$_2$ agree with experimental spectra and depart from the rigid-band picture of 2H-NbS$_2$.
  The physical origin of the band shift can be readily traced to big Co-Nb orbital overlap, $t_{Co}\approx 0.23$ eV, emerging as the dominant hybridization integral in the tight-binding parametrization of the DFT results in  Co$_{1/3}$NbS$_2$.
  Indeed, the position in energy of the bonding Nb band at the Brillouin zone center is susceptible to changes in the $t_{Co}$ parameter.
  At the same time, the position of the antibonding band is saved from the shift for symmetry reasons.
  In short, the large $t_{Co}$ parameter very much increases the splitting between antibonding and bonding bands in Co$_{1/3}$NbS$_2$ in comparison to 2H-NbS$_2$.

  On the other hand, in Fig.~\ref{figEM-A} (a) one observes significant reconstruction of spectra calculated for Co$_{1/3}$NbS$_2$ relative to 2H-NbS$_2$ conduction bands, with the bands splitting being particularly pronounced around the K and M points, at the boundary of the first Brillouin zone of Co$_{1/3}$NbS$_2$.
  The splitting is not seen in experimental spectra.
  The dominant source of the reconstruction can be traced to the variation of the in-plane Nb-Nb hybridization integrals imposed by the antiferromagnetic superstructure and strong spin polarization at Co atoms and in their vicinity.
  The previous statement can be verified by exploring other magnetic structures, e.g., the ferromagnetically ordered state, or by calculating the unfolded spectra upon reducing the spatial variation of Nb-Nb hybridization integrals within the TB parametrization, leaving the other TB parameters unchanged. In all these cases, the Nb 4d conduction bands remain effectively continuous throughout the large Brillouin zone.

  Interestingly, and more importantly, no extra features appear at the Fermi level in the same region of the $k$-space.
  The signal calculated at the Fermi level is shown in the inset of Fig.~\ref{figEM-A}.
  With no signal around K and M points, the spectrum at the Fermi level bears no marks of the $\beta$-band.
  The only qualitative departure from the picture of rigidly-filled 2H-NbS$_2$ bands appears though one Fermi-surface ring encircling the $\Gamma$ point, instead of two, expected for 2H-NbS$_2$.
  Of course, the absence of the second ring is related to the shift of the maximum of the Nb $4d$ bonding band below the Fermi level, related to Co-induced interlayer hybridization, discussed already.

   \begin{figure}[t!]
  \includegraphics[width=0.45\textwidth]{Figure9.pdf}
  \caption{(Color online). The unfolded spectra of the system modeled through tight-binding reparameterization, with the parameters initially taken from our DFT/Wannier90 calculation. Very few modifications, detailed in the text, are inspired by studies of the effects of strong electron correlations in other systems. The model includes Niobium and Cobalt levels near the Fermi level, whereas the Sulphur bands, being further away from the Fermi level, are not included. The image plots the unfolded spectral density along  the M$_0$$\Gamma$K$_0$ line in $k$-space. The insets shows the spectral density distribution at Fermi energy over the $k_z=0$ plane in the Brillouin zone. The color bar indicates the intensity scale.}
  \label{figEM-B}
  \end{figure}

  \subsection{Beyond DFT}

    For a particular magnetic state offered as a seed, the spin-polarized DFT calculation tends to self-consistently determine the magnetic state on Co atoms in the specific magnetic configuration and produce the appropriate electronic bands.
  The calculation results with Co atoms with sizable magnetic moments, with particular lower and upper "Hubbard states" populated by spin up or spin down electrons.
  The resulting bands conform the TB description where, apart from the spin character at particular Co orbitals, the other parameters stay essentially unaltered among different magnetic states\cite{SIref}.
  The TB parametrization of electronic bands in various magnetic states leads to results where
  the hybridization integral between Co and Nb orbitals ($t_{Co}$) is approximately two times bigger than any other hybridization integral in the model, including those responsible for the Nb $4d$ bands dispersions in directions parallel and perpendicular to layers.
  Further on, the separation between spin-down and spin-up $3d$ states at Co atoms below and above the Fermi level is one order of magnitude bigger than any hybridization integral in the TB model and approximately six times bigger than the Co-Nb orbital energy level separation.
  The Nb orbital energy level and the calculated Fermi energy lie in-between energy levels of the full Co orbital of one spin projection, and the empty Co orbital of the opposite spin projection.
  This description conforms with the picture of a strongly correlated electron system.
  It may be safely said that the DFT producing an array of local magnetic moments strongly hybridized  to relatively narrow metallic bands is a good indication of a strongly correlated electron system.
  Conversely, strongly correlated electron systems are poorly treated by common DFT or by any approach relying on representing its wavefunction as the determinant of whatever single-particle states.
  Whereas some properties may be caught better than others, the description of low energy dynamics of such a mixture of magnetic moments and itinerant electrons is obliged to fail in such approaches.

  The methods able to deal with strongly correlated electron systems have been developing intensively in recent decades.  A proper theoretical framework for the present problem may be possibly sought within the combination of the density functional theory and the dynamical mean-field theory (DFT+DMFT)\cite{Georges1996, Kotliar2006},  with the Hund's rule coupling properly included to account for the spin-3/2 Co state\cite{Medici2011}.
  With the implementation particular to Co$_{1/3}$NbS$_2$ still being awaited for, the poor man's alternative would be to apply the qualitative recipes based on previous works.
  The previous treatments of centers with big local Coulomb repulsion in contact with conducting electrons, appearing within the Anderson impurity model, in heavy fermion systems, and electronic models for copper oxide superconductors, provide the hint.
  Several approaches to strongly correlated electron systems result in effectively reducing the hopping integral between conduction band states and the large-$U$ orbital, accompanied by the big shift in the orbital energy at the strong-U center level towards the Fermi level\cite{Kotliar1988,Coleman1984,Coleman2007,Niksic1995, Tutis1994,Tutis1997}.
  These two changes, appearing within the slave-boson approaches to strongly correlated electron systems, are possibly representing the shortest path to what is called the Kondo-Anderson-Suhl resonance in systems with magnetic impurities, and to resonance bands appearing at the Fermi level in crystalline systems.
  Physically they are related to the electron of one spin projection blocking the electrons of other spin projection from hopping into the large-$U$ orbital, resulting in the formation of the low-energy resonance related to local spin-flip process.
  The width of the resonance (band) depends very much on the initial parameters like bare overlap integral.  It is expected to be very much smaller in the systems involving $f$ orbitals than in the systems based on $d$ orbitals.
  In our case, these changes amount to reducing $t_{Co}$ and shifting the Co orbital energy level towards the Fermi level.
  Also, all Co are to be treated equivalently, to account for the system without magnetic order.
  Performed together, the changes in $t_{Co}$ and Co orbital energy can keep the position of the Nb bonding-band below the Fermi level, in the place indicated by experimental spectra.
  At the same time, the reparameterization shifts the bottom of the narrow Co-band to the Fermi level.
  The resulting spectra are shown in Fig.~\ref{figEM-B}. The signal at the Fermi level shown in the inset  resembles a great deal to the $\beta$-band observed experimentally and shown in Fig.~\ref{figk1}.
  The Nb bands in Fig.~\ref{figEM-B} run cautiously throughout the zone, similarly to measured spectra.
  Not unseen in previous instances in strongly correlated electron systems, the required renormalizations of two tight-binding parameters are relatively big,
  with the Co-Nb level separation requiring reduction from 0.83 eV to approximately 0.25 eV,
  whereas the Co-Nb hybridization demands the resizing by the factor of one-half.
  Although the shift in energy level, much studied within the slave-boson approach to strongly correlated systems, produces the resonance band at the Fermi level, it should be kept in mind that Fig.~\ref{figEM-B} represents only the partial result.
  The figure represents the spectrum related to auxiliary fermion fields, whose features remain present upon returning to real fermions, but accompanied by significant transfer of spectral weight into the energy range of the original energy level above the Fermi level\cite{Tutis1994,Niksic1995,Tutis1997}.
  As announced, a more elaborate study of this particular topic is yet to follow.

  It remains to comment upon another possible mechanism being able to influence the TB parameters in the same direction. This mechanism is the relaxation of crystal layers, operating only in the close vicinity of the crystal surface.
  Indeed, the increase in the interlayer separation is expected to decrease the Co-Nb hybridization integral and the separation between Co and Nb energy levels.
  The latter would come from the change in electrostatic potential of the electron in the Co orbital, as the Co atom moves further away from negatively charged Nb atoms.
  We have not studied numerically the surface relaxation in Co$_{1/3}$NbS$_2$, and it remains to be seen if the required significant changes in parameters may be accounted for in this way.
  Also, one must keep in mind that even within the scenario based on surface relaxation, the problem of strong correlations remains present and unattended, both in bulk and near the surface.

\section{Conclusions}

 We have presented the first ARPES study on Co$_{1/3}$NbS$_2$ accompanied with a detailed analysis of the observed electronic structure.
   At first, the measured electronic structure shows remarkable similarity to the parent material 2H-NbS$_2$, whose electronic structure is known from previous measurements and is well described by DFT electronic structure calculations.
  In the observed spectra, we find no signs of the 2H-NbS$_2$ bands getting folded or gapped at the boundary of the Brillouin zone of Co$_{1/3}$NbS$_2$, i.e. the super-lattice of 2H-NbS$_2$ imposed by intercalation.
  Motivated by this and the fact that the rigid-band picture has been ruling the field for decades, we systematically compare the features observed in Co$_{1/3}$NbS$_2$ with those appearing in calculated 2H-NbS$_2$ spectra.
  The DFT calculation for 2H-NbS$_2$ with additional 4/3 electrons per unit cell, simulating the charge transfer of two electrons per Co into NbS$_2$ layers, produces the shift in Fermi level of approximately 0.5 eV and accounts rather well for its observed position relative to what we identify as the 2H-NbS$_2$ bands.
  All this goes in favor of the 2H-NbS$_2$ rigid band picture.

  However, it turns out that several deviations from the rigid band picture can entirely change our view of magnetically intercalated TMD's.
   One of these deviations corresponds to the local maximum of the bonding Nb $d$ band being found 0.3 eV below Fermi level at $\Gamma$ point, whereas it is expected to stand above the Fermi level in the rigid band picture.
  The observed change in the bonding band corresponds to very strong Co-Nb hybridization, bigger than any other parameter shaping the 2H-NbS$_2$ conduction bands.
  This overwhelmingly strong hybridization questions the applicability of the low-order perturbative concepts to magnetic interactions in intercalates\cite{Sirica2020}, often assumed to govern the magnetic states in intercalates.
  The "$\beta$"-band is the second important deviation from the 2H-NbS$_2$ electronic structure.
  This band is not foreseen by any measurements or DFT calculations in 2H-NbS$_2$ or Co$_{1/3}$NbS$_2$.
   In our spectra it appears as the necklace of shallow electron pockets centered at six K-point corners of the first Brillouin zone of Co$_{1/3}$NbS$_2$.
  The strong electron correlations impose as the possible explanation for the appearance of this new band at the Fermi level.
  The strong hybridization and unexpected shallow band at the Fermi level speak together in favor of Co$_{1/3}$NbS$_2$ being considered a strongly correlated electron system,  with the coupling between metallic and magnetic layer playing the essential role.
  This signifies the substantial paradigm shift in magnetically intercalated TMD's, to be explored and confirmed through further experimental and theoretical work.

\section*{Acknowledgements}

Y. U. thanks Z. Chen, J. Dong, E. Papalazarou, and L. Perfetti for their experimental support to perform preliminary ARPES measurement using He I$\alpha$ resonance line, and O. Bari\v{s}i\'{c} for helpful discussions. This work has been supported in part by the Croatian Science Foundation under the project numbers IP-2016-06-7258 and IP 2018-01-7828. These researches have been performed at the National synchrotron radiation centre SOLARIS at the UARPES beamline (proposals No. 181PH009 and 201046). The experiment has been performed thanks to the collaboration of the SOLARIS staff. The research leading to this result has been supported by the project CALIPSOplus under the Grand Agreement 730872 from the EU framework programme for research and innovation HORIZON 2020. The work in Lausanne was supported by the Swiss National Foundation. The work at the TU Wien was supported by the European Research Council (ERC Consolidator Grant No 725521), while the work at the University of Zagreb was supported byproject CeNIKS co-financed by the Croatian Government and the European Union through the European Regional Development Fund -Competitiveness and Cohesion Operational Programme (Grant No. KK.01.1.1.02.0013). I.B., W.T., and M.A.G. acknowledge financing from the Polish National Agency for Academic Exchange under "Polish Returns 2019" Program, PPN/PPO/2019/1/00014, and subsidy of the Ministry of Science and Higher Education of Poland.

P.P. and  Y.U. equally contributed to the paper.

\section{Appendix}

\subsection{The $\beta$-band and the $k_z$ dispersion}

  \begin{figure}[b!]
  \includegraphics[width=0.5\textwidth]{Figure10.pdf}
  \caption{(Color online). (a) The photon energy dependence of the momentum distribution curves (MDCs) along the $\Gamma$K$_0$ direction at the Fermi level. The MDCs are taken at the same photon energies as in Fig.~\ref{nfig5}. The same normalization applies as in Fig.~\ref{nfig4}. (b) ARPES intensity plot of the $k_z$-$k_{\Gamma K_0}$ band dispersion at Fermi level. $\Gamma$ and A high symmetry points of the Brillouin zone are also indicated. Two vertical dashed lines shown in cyan in both panels represent the boundary of the Brillouin zone of Co$_{1/3}$NbS$_2$ and correspond to M point at $k_z$ = 0.}
  \label{figA1}
\end{figure}
     Fig.~\ref{figA1}(a) shows the momentum distribution curves (MDCs) at the Fermi level, measured by using horizontally polarized photons at various photon energies.
   Fig.~\ref{figA1}(b)  shows the ARPES intensity plot at the Fermi level within the rectangular section in $k-$-space, extending along  $k_z$ and $k_{\Gamma K_0}$ directions. This plot is also produced from the ARPES spectra taken at various photon energies.
    In Fig.~\ref{figA1}(a) the antibonding Nb 4$d$ band can be observed at all energies at 0.3 \AA$^{-1}$. It also shows as sharp line in Fig.~\ref{figA1}(b).
     The signal related to the $\beta$-band is observed in both panels along the vertical cyan lines marking the boundary of the first BZ of Co$_{1/3}$NbS$_2$.
  The latter signal dominates Fig.~\ref{figA1}(b).

  \begin{figure*}[t!]
  \includegraphics[width=\textwidth]{Figure11.pdf}
  \caption{(Color online). (a) DFT calculated electronic bands of 2H-NbS$_2$ with DFT relaxed lattice parameters and (b) DFT calculated electronic band of 2H-NbS$_2$ with additional 2/3 electrons per Nb atom and the lattice parameters borrowed form DFT-relaxed Co$_{1/3}$NbS$_2$ structure. Blue color indicates Niobium orbital character while yellow color indicates Sulphur orbital character.}
  \label{figA2}
  \end{figure*}

  The momentum along the $z$ direction for Fig.~\ref{figA1}(b) is calculated using the expression in Eq.~(\ref{eq:kz}).
   For the parameter V$_0$ in Eq.~(\ref{eq:kz}) we adopt the value proposed previously for the sister compound Cr$_{1/3}$NbS$_2$, i.e. $V_0$ = 14 eV\cite{Sirica2016}.
   With this choice of $V_0$, and for the range of photon energies used in measurement, the $k_z$ extends from around $\Gamma_8$ to $A_9$.
  Here, as usual, $\Gamma_n$ marks the point at $(0,0, 2\pi/c \times n)$ in $k$-space, whereas $A_n$ stands for the midpoint between $\Gamma_n$ and $\Gamma_{n+1}$.
   It may be remarked that the periodicity of $2\pi/c$ along $k_z$ is not observed in Fig.~\ref{figA1}(b).
  Some possible reasons have been already discussed out in Sec. ~\ref{sec:discussion}, in relation to Fig.~\ref{nfig4}.
  In addition, the fact that there are two Co layers per unit cell along $z$-axis leads to the periodicity of $4\pi/c$ for the particular signal type, similar to $8\pi/c$ periodicity observed for S signal in NbSe$_2$ \cite{weber2018}. In that respect, like in Ref.~\onlinecite{weber2018}, a wider photon energy range may be needed to observe the periodicity in $k_z$.
  Apart from the absence of the simple periodicity in the signal intensity, we do not observe significant shifts in the position of signals related to the anti-bonding band and the $\beta$-band.

\subsection{DFT calculations in 2H-NbS$_2$}\label{sec:AppDFT1}

  The paradigm of rigid band shift has been ruling the field of magnetically intercalated TMDs for decades.
  Therefore, we made a long way to compare the measured electronic structure of Co$_{1/3}$NbS$_2$  with the electronic structure of the parent compound 2H-NbS$_2$.
  Here we show two of several DFT calculations that we made for the purpose of this comparison.
  First, we show the DFT results for the electronic band structure of 2H-NbS$_2$, where the unit cell was obtained by relaxing the atomic forces within the DFT calculation.
  This electronic band structure is shown in Fig.~\ref{figA2} (a). Here, the electronic charge transfer from Co atoms to NbS$_2$ layers is not included in any way.
  After the rigid band shift, introduced to account for the transfer, this electronic structure does not account for all experimentally observed features. All points of disagreement detailed in the main text apply.
  Second, we address the electronic structure of  2H-NbS$_2$ where the unit cell lattice parameters are taken from DFT relaxed AF ordered Co$_{1/3}$NbS$_2$.
  Also, 2/3 electrons per Nb are added to NbS$_2$ layers from the outset to account for the charge transfer from Co ions.
  As usual, these extra electrons were compensated by an appropriate positive homogenous background charge.
  These results are shown in Fig.~\ref{figA2} (b).
  Entirely expected, the added electrons produce an immediate shift of NbS$_2$ bands towards higher binding energies.
   Apart from the shift, the main difference between the two panels in Fig.~\ref{figA2} is energy separation between bonding and antibonding Nb 4 $d$ bands and position of highest laying Sulphur band.
  This result shown in Fig.~\ref{figA2} (b) was choosen for comparison with experimental spectra in Fig.~\ref{fig2}, panels (d) and (e).  In Fig.~\ref{fig2} the calculated bands were further shifted 0.1 eV to higher binding energy to improve the overall match to experimental results.
   The bonding Nb $4d$ band, observed below Fermi level in ARPES spectra at the $\Gamma$ point, remains above the Fermi level in both calculations presented here, even after the rigid band shift.
    The additional point to be taken from Figs.~\ref{figA2} (a) and (b) is the relatively high sensitivity of the top Sulphur bands, in shape and width, to small changes of the interlayer distance.

\bibliographystyle{apsrev4-2}

redpajama_set_name: RedPajamaArXiv


ChiIL Mama : Happy Blue Year--With Blue Man Group!
In 2011 ChiIL Mama was quoted in the Blue Man Group ads! Blue Man Group retooled and updated their show in a fun, new way, and we highly recommend checkin' it out.
Here's ChiIL Mama's full review.
As we get closer to the end of the year, there are plenty of parents and families looking for something to do together to ring in the New Year. Say goodbye to 2011 with one of Chicago's most celebrated entertainment shows, the Blue Man Group.
With shows at 4, 7, and 10 p.m. there are shows perfect for the entire family. The 7 and 10 p.m. shows feature champagne and sparkling cider toasts as well as celebratory party favors. Families attending the 10 pm show will welcome 2012 with the Blue Men as they countdown to the New Year and play Auld Lang Syne on the custom-made instrument, the Tubulum.
the Perfect Option for the Entire Family to Celebrate the Holiday.
Blue Man Group, the critically hailed theatrical phenomenon on stage at Chicago's Briar Street Theatre (3133 N. Halsted Street), is wishing Chicago a Happy 2012 with three performances on New Year's Eve.
Blue Man Group's production provides its audience with a unique and thrilling multi-sensory experience that blends innovative theatrical spectacle and dynamic original music with hilarious comedy, art, technology and science to create a performance experience unlike any other.
In the show, the Blue Men encounter a variety of environments to discover, engage with and explore of-the-moment situations with cutting-edge technology. Many of the signature scenes that have made Blue Man Group one of today's best-loved theatrical productions have been in the show since its opening, though new material has been integrated. Newer passages include Blue Men interacting with "GiPads;" a funny and perceptive look at contemporary communication vehicles; and a pulsating new finale featuring an original Blue Man Group music score.
Currently, Blue Man Group theatrical shows can be seen in New York, Boston, Chicago, Las Vegas, Orlando, Berlin, Tokyo, and on tour throughout the U.S. Blue Man Group can also be seen onboard the new Norwegian Epic by Norwegian Cruise Line – the Official Cruise Line of Blue Man Group.
Blue Man Group's appeal is multi-generational, with several projects specifically designed for young people, including "Making Waves," a popular touring exhibit for children, and the recently launched national "Invent an Instrument" competition.
Tickets prices for the 4, 7, and 10 p.m. shows on New Year's Eve are $55 - $75. Tickets may be purchased at the Briar Street Theatre by calling the box office at (773) 348-4000; by calling Ticketmaster at (800) 982-2787; at all Ticketmaster ticket centers or via the Internet at www.ticketmaster.com/bluemanchicago. For more information, visit www.blueman.com/chicago.


text:
The moon is shrinking: NASA records lunar earthquakes that prove it's still tectonically active as it cools and contracts
The moon's surface is scarred with 'scarps' which are steep step-like cliffs
They are formed when the moon's interior cools and the exterior contracts
This causes the brittle surface to crack and form the long scars on its surface
Analysis has found this process to be ongoing and evidence the moon is shrinking
By Joe Pinkstone For Mailonline
The moon experiences its own version of Earthquakes which are causing it to shrink, scientists have found.
So-called 'moonquakes' are a result of it being tectonically active and they are forcing our natural satellite to wrinkle 'like a raisin'.
Its interior is cooling which causes the surface to contract, but the brittle surface cracks and forms step like cliffs called 'scarps'.
These are roughly ten yards high and a few miles long and resemble a giant stairway on the lunar surface.
They were first discovered more than 50 years ago by the Apollo astronauts and analysis has found them to be still forming.
This prominent thrust fault is one of thousands discovered on the moon by NASA's Lunar Reconnaissance Orbiter (LRO). These faults resemble small stair-shaped cliffs, or scarps. Scarps form when one section of the moon's crust (left-pointing arrows) is pushed up over another section (right-pointing arrows) as the moon's interior cools and shrinks
Scientists superimposed epicentre location data onto images of the scarps from NASA's Lunar Reconnaissance Orbiter (LRO).
At least eight of the 28 scarps recorded from 1969 to 1977 likely resulted from true tectonic activity, researchers claim.
This is the movement of plates in the lunar crust which create 'thrust faults'.
They say these scars on the surface of the moon are more likely to have formed from moonquakes than from asteroid impacts or rumblings deep within the interior.
NASA hopes to return to the moon in the next few years and the ground-breaking finding could speed up their plans.
Co-author Professor Nicholas Schmerr, a geologist at Maryland University, said: 'We found a number of the quakes recorded in the Apollo data happened very close to the faults seen in the LRO imagery.'
The photographs also show physical evidence of geologically recent fault movement - such as landslides and tumbled boulders.
He said: 'It's quite likely the faults are still active today.
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'You don't often get to see active tectonics anywhere but Earth - so it's very exciting to think these faults may still be producing moonquakes.'
The discovery of young faults less than 50 million years old by the LSO's camera in 2010 has been interpreted as evidence of lunar tectonic activity.
US and Canadian researchers examined quakes recorded by seismometers at the landing sites of Apollo 12, 14, 15 and 16.
Using an algorithm they found the epicentres of eight of the quakes - more than a quarter - were within 19 miles of scarps visible in the LRO images.
This was close enough to conclude the Moon is currently tectonically active.
The LRO's camera has identified thousands of the strangely shaped cliffs - stretching from the south to north poles - and found the moon is still shrinking.
The Apollo instruments recorded their last quake shortly before they were retired in 1977.
But the moon is likely experiencing quakes to this day, say the researchers.
The shallow quakes would have ranged in magnitude from about two to five on the Richter scale if they occurred on Earth.
This would be enough to damage buildings and other structures.
The researchers also found six of the eight quakes happened when the moon was at or near its apogee - the point in the moon's orbit when it is farthest from Earth.
This is where additional tidal stress from Earth's gravity causes a peak in the total pressure on the moon's crust - making slippage along the thrust faults more likely.
Lead author Senior Scientist Dr Thomas Watters, of the Centre for Earth and Planetary Studies at the Smithsonian Institution in Washington, said: 'We think it's very likely these eight quakes were produced by faults slipping as stress built up when the lunar crust was compressed by global contraction and tidal forces, indicating the Apollo seismometers recorded the shrinking moon and the moon is still tectonically active.'
The moon wrinkles as its interior cools and shrinks - much as a grape does as it dries to become a raisin.
But unlike the flexible skin on a grape the moon's crust is brittle - causing it to break as the interior shrinks.
This results in thrust faults where one section of crust is pushed up over an adjacent section.
The shallow quakes would have ranged in magnitude from about two to five on the Richter scale if they occurred on Earth. This would be enough to damage buildings and other structures (stock)
The LRO has imaged more than 3,500 fault scarps on the moon since it began operation in 2009.
Some of these images show landslides or boulders at the bottom of relatively bright patches on the slopes of fault scarps or nearby terrain.
Because weathering gradually darkens material on the lunar surface, brighter areas indicate regions that are freshly exposed by an event such as a moonquake.
Other LRO fault images show fresh tracks from boulder falls, suggesting that quakes sent these boulders rolling down their cliff slopes.
Such tracks would be erased relatively quickly, in terms of geologic time, by the constant rain of micrometeoroid impacts on the moon.
With nearly a decade of LRO imagery already available and more on the way in the coming years, the team would like to compare pictures of specific fault regions from different times to look for fresh evidence of recent moonquakes.
Professor Schmerr said: 'For me, these findings emphasise we need to go back to the moon.
'We learned a lot from the Apollo missions, but they really only scratched the surface.
'With a larger network of modern seismometers, we could make huge strides in our understanding of the moon's geology.
'This provides some very promising low-hanging fruit for science on a future mission to the moon.'
The study was published in the journal Nature Geoscience.
WHAT ARE MOONQUAKES?
So-called 'moonquakes' are a result of it being tectonically active and forcing our natural satellite to wrinkle 'like a raisin' - creating step like cliffs called 'scarps'.
At least eight of the 28 recorded from 1969 to 1977 likely resulted from true tectonic activity, researchers claim.
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redpajama_set_name: RedPajamaCommonCrawl


Simulation result of a Mach 0,5 oblong jet with a nozzle element ratio of 5 and a Reynolds variety of 2000 in keeping with the slim nozzle width are awarded. the focal point is at the move improvement within the near-nozzle area and at the flow-induced acoustic radiation from the jet. Perturbations in response to so much risky modes of the laminar influx pro_le estimated by way of linear balance conception are enforced on the inflowto start up transition.
The Visibooks advisor to Linspire Five-O covers Linspire, the main uncomplicated model of Linux, widely-used via colleges. It presents a company starting place within the basics of utilizing Linspire, together with utilizing the internet and electronic mail.
A complete visual inspection should be made t o eliminate this possibility. Where single insulation is used, all connections between the rotor and the frame a t the lower end of the machine must be removed to test the bearing insulation, or each joint must be isolated and tested individually. 7 Installation of Lubrication System. Every section of pipe forming a part of the lubrication system should be freed of scale, reamed a t both ends, and blown out with compressed air or steam before being connected.
The elevation of a self-oiled bearing must be such t h a t the oil groove, if any, is completely covered by the opposite member. The elevation must also be such that, when the rotor is raised to its maximum upward position by the jacks, the bottom of the journal will be below the center of the guide bearing. After the bearing has been assembled, the remaining parts of the oil reservoir are added. Clearances between these parts and the shaft must be adequate to prevent rubbing. 9 Check of Insulation Against Shaft Currents.
If the rotation check by method 1 is used, it shall be performed during the erection of the generator t o avoid subsequent disassembly of the machine. 11 Shaft-Plumb and Straightness Check. This is a plumb-wire check of the straightness and plumbness of the combined generator and turbine shafts. The use of four plumb lines spaced 90 degrees apart around the shaft i s recommended. T h e readings should be taken from the same points on each shaft t h a t were used during the factory runout check.


Our AutoScheduler makes it Easy for You to interact with your members - with online communication and scheduling tools that are fast, powerful, and easy-to-use. Team Schedule Publisher makes it Easy for All of your coaches, player and parents to stay informed - anytime, anywhere.
With PlayAYF, managing your teams communication has never been easier. Our team communication service allows coaches, players, and parents to stay connected from any internet connected computer or mobile device.
AutoScheduler improves your team communication and eliminates the hassle of team management. Publish game and practice schedules to your members with PlayAYF's communication software.
Need to cancel a game/practice due to bad weather? PlayAYF Football Scheduler gives you the communication tools to alert all your team members several days in advance or on "short notice." This team communication service will help you eliminate the need to publish schedules on spreadsheets or word files, as each schedule is associated with specific team(s) in the PlayAYF online system.
Home games, away games, practices, or "other"
The schedules are directly linked to team(s), and since the system knows the relationship between the two - instead of having to navigate through everyone's schedule, players and parents only see their schedule.


No one told John Kasich a right-wing militia had taken over a government building until today.
On Monday, Kasich was asked what he thought about the biggest news of the last few days: the Bundy militia seizing an Oregon building with the motivation, according to a sheriff's press release, "to attempt to overthrow the county and federal government in hopes to spark a movement across the United States." Kasich had no idea what the reporter was talking about.
At the very least, we now know that the candidate does not waste a lot of time on Twitter. Or watching the news. Or reading news websites. John Kasich: cord cutter.


▷ Best Cheap Gaming Headsets Review 2019 » Best Budget!
"Storm the front!" "Taking fire, need assistance!" Have you ever been online to play and wonder why you were so mercilessly quickly defeated by your opponent's team in Shooter XY? Lack of communication could be one of the reasons. And that's where the gaming headset comes in. Exchange ideas with your teammates! Whether strategy game, MMORPG or shooter, you can simply support your team more concentrated if you do not have to bend over to the table microphone. Or even worse, not having any. Surround sound or stereo can also help you locate the sources of noise in games much better.
You want to buy a cheap gaming headset? Let us give you a brief overview of the products of 2018 in this gaming headset comparison. How to find your personal gaming headset comparison winner.
What is a gaming headset? And why do I need that?
(Surround) sound to suit your taste and game choice.
The G430 from PC specialist Logitech is a Dolby technology headset with 7.1 surround sound. The seven audio channels plus one for low-frequency effects create a breathtaking sound field that should lead the wearer directly into the game. Furthermore, an exact location of the opponent is possible. The microphone suppresses annoying background noises, so the instructions are always clearly heard, even during fierce battles. If the microphone is not used, turn it upwards.
The G430 offers an almost sensational sound for its price. In battles, shots look extremely realistic and you really feel like you're in the middle of the game, we can see from customer reviews on Amazon. The location of the opponent also works perfectly. The headset is also suitable for listening to music, but here you can notice the rather bass-heavy orientation. But if you don't mind, you will be satisfied with the sound result in this area as well. The microphone is top, it couldn't be better in this price range.
The headset adapts well to the head shape and can be adjusted exactly, we also take from the customer reports. In addition to the comparatively low weight, the buyers also liked the design, because over-ear headphones are simply super comfortable. As expected, the workmanship of the G430 is almost first-class, we have not found any weak points.
In addition to the headset, a USB adapter and operating instructions are included. That's a bit lean, a bag would have been nice, for example. The special thing about this model is its good sound.
The Sennheiser PC 360 G4ME is primarily aimed at pro gamers, as it was developed together with the eSport team mTw. The headset scores with an open design that keeps you cool no matter how stressful the situation may be. The Pro microphone and quick-access controls, which you need for playing, chatting, listening to music and watching video, are also convincing. The noise-canceling microphone reduces ambient noise and automatically mutes when turned upwards. The headset is available in black.
The sound of the PC 360 arrives clearly and precisely in the own ear, the heights are unfortunately a little too sharp, as the test reports to this model have taken. But the headset scores with a very good spatial positioning. The Sennheiser is therefore perfect for gaming. Music sounds a little chilly, they say, which is why audio purists will have their problems with this sound orientation.
The Sennheiser generously surrounds the ears with his auricles, but he presses a little on the jaw joint, while some customers on Amazon report. Overall, however, the seat of this model is already good to very good. The robust construction ensures long operating times, the workmanship is completely Sennheiser-like at a high level, we also take from the evaluations. We award 4 out of 5 stars.
The scope of delivery of the PC 360 G4ME is minimal, there is only a short manual in the box next to the headset itself, unfortunately we could not make out a bag or something else. The special feature of this model is its consistent focus on games.
The HyperX Cloud II Gaming Headset is an asset to any gaming freak. The tool is produced by Kingston Technology. The Hyper X gaming headset from Kingston Technology is part of Kingston's Cloud II series.
It is delivered to the buyer in a bundle with the corresponding software and, when ordered via Amazon, is delivered within just a few days. The trendy and modern gaming headset weighs 272 g according to the manufacturer. The color is red. Kingston Technology puts the dimensions at 27.9 x 22.9 x 10.2 cm.
Kingston Technology's Hyper X Cloud gaming headset features a redesigned audio control box. By the way, this is also able to serve the gamer as a USB sound card.
HyperX Cloud 2 ControlThis audio control box amplifies both the audio and voice signals in the HyperX Cloud II. As a result, Kingston Technology's Hyper X Cloud gaming headset offers players an unprecedented sound and gaming experience.
It has already been mentioned that this unique gaming headset can also offer you a lot of wearing comfort. For example, the gaming headset has its own special ear cushions, which are 100% made of the latest memory foam.
The headphone earcups are generally interchangeable, so that different sound profiles are ultimately possible due to different surfaces.
But a modern and powerful gaming headset like the Hyper Cloud X also depends on its design and the equipment and accessories that come with it.
The accessories are designed to allow and guarantee the use of this gaming headset in various environmental conditions. For example, the scope of delivery includes an aircraft adapter, a wide variety of imitation leather and suede upholstery and a suitable mesh bag for mobile use on the move.
What types of gaming headsets are available?
Every headset is different. Some like their massive sound in the bass range, or their pleasant upholstery. Others, on the other hand, have additional features such as better detection of opponents in games. Others have completely committed themselves to the wireless idea in design and implementation.
Due to the wealth of different features, in this gaming headset comparison we divide all headsets into two product categories based only on what is probably the most striking feature: wired and wireless.
Are usually cheaper with the same other equipment than wireless models. In addition, it is often lighter, since no battery needs to be installed. The only disadvantage is the limited room for movement or disturbing cables on the floor, lap, chair or desk.
You can read more about the difference between the three types here, for example. In general it can be said that from "open" to "half-open" to "closed" the bass reproduction and the shielding of external noise is improved. Most gaming headsets use the "Closed" design for better immersion.
The type of microphone mounting is also relevant. While some headsets use rigid microphone arms, others offer a flexible and therefore customizable gooseneck mount. This can then be freely positioned, similar to the principle of some lamp stands.
Less potential noise: the digital signals are only converted in the headset itself. Irradiation from sources of interference is therefore less likely.
Only one USB plug is required.
However, the built-in sound chip is almost always inferior to a dedicated sound card. If you have a high-quality sound card, you should connect your gaming headset directly to it via a jack!
Potentially more sound interference possible, as the analog (and thus more interference-prone) signal is routed along the entire cable route. However, high-quality headsets usually have sufficient cable shielding.
The direct connection to the internal sound chip (integrated on the mainboard or in an additional sound card) means that you are not dependent on the sound quality of a headset's own sound processor.
Without front audio connections, it takes longer to connect than USB headsets.
If you wear your closed headset for a long time while playing online, this can lead to heat build-up in your ears, especially with your headphones closed. An additional padding kit can be ordered for most headsets. This allows you to quickly change the upholstery set between two rounds. Or after one year, if the first signs of wear occur.
It may also be advisable, for example after long WoW, CS-GO, LoL or CoD sessions, to carefully wipe off the ear cushions with a damp cloth and clean them. Make sure, however, that no moisture gets to the membranes! So your headset remains the best gaming headset for you for a long time.
If your new gaming headset gives you an uncomfortably cramped head feeling, or even headaches, there is something wrong. Check if your headset may be set too tightly. Maybe the temple of your glasses presses too hard on your temples through the headset. Try different settings and wearing styles.
If this does not improve, try another headphone! A change of design, i.e. from closed to semi-open, can also lead to an improvement.
How to connect a gaming headset?
Either you need a free USB port on your device, or two 3.5 mm jacks. These are usually marked in red (micro) and green (headphones). Xbox One, PS4 and Gaming PC have different ways to connect a headset.
Which gaming headset is the best gaming headset?
Wearing method: open, semi-open, or closed?
Which Gaming Headset for PS3 / PS4 / Xbox 360/ Xbox One?
Xbox360: Official help from Microsoft Xbox Support.
Xbox One: Official help from Microsoft Xbox Support.
PS4: The PS4 supports Bluetooth, USB and jack headsets. So you have a free choice. To use a 3.5 mm jack headset you need an adapter.
Gaming Headset: wireless or wired?
Wireless convenience makes headsets expensive in no time. So consider carefully whether less cable clutter and higher mobility (within a maximum of 12 metres) are worth this surcharge. In this gaming headset comparison, there are significantly fewer wireless models than those with cables, which also reflects the market situation.
1 What is a gaming headset? And why do I need that?
5 What types of gaming headsets are available?
9.1 How to connect a gaming headset?
9.2 Which gaming headset is the best gaming headset?
9.3 Which Gaming Headset for PS3 / PS4 / Xbox 360/ Xbox One?
9.4 Gaming Headset: wireless or wired?