  Recently discovered kagome superconductors AV3Sb5 (A=K, Rb, Cs) provide a
fresh opportunity to realize and study correlation-driven electronic phenomena
on a kagome lattice. The observation of a 2a0 by 2a0 charge density wave (CDW)
in the normal state of all members of AV3Sb5 kagome family has generated an
enormous amount of interest, in an effort to uncover the nature of this CDW
state, and identify any "hidden" broken symmetries. We use
spectroscopic-imaging scanning tunneling microscopy to reveal a pronounced
intensity anisotropy between different 2a0 CDW directions in KV3Sb5. In
particular, by examining the strength of ordering wave vectors as a function of
energy in Fourier transforms of differential conductance maps, we find that one
of the CDW directions is distinctly different compared to the other two. This
observation points towards an intrinsic rotation symmetry broken electronic
ground state, where the symmetry is reduced from C6 to C2. Furthermore, in
contrast to previous reports, we find that the CDW phase is insensitive to
magnetic field direction, regardless of the presence or absence of atomic
defects. Our experiments, combined with earlier observations of a stripe 4a0
charge ordering in CsV3Sb5, establish correlation-driven rotation symmetry
breaking as a unifying feature of AV3Sb5 kagome superconductors.

Superconductivity;Materials Science;Strongly Correlated Electrons