  Kitaev spin liquid (KSL) system has attracted tremendous attention in past
years because of its fundamental significance in condensed matter physics and
promising applications in fault-tolerant topological quantum computation.
Material realization of such a system remains a major challenge in the field
due to the unusual configuration of anisotropic spin interactions, though great
effort has been made before. Here we reveal that rare-earth chalcohalides REChX
(RE=rare earth, Ch=O, S, Se, Te, X=F, Cl, Br, I) can serve as a family of KSL
candidates. Most family members have the typical SmSI-type structure with a
high symmetry of R-3m and rare-earth magnetic ions form an undistorted
honeycomb lattice. The strong spin-orbit coupling of 4f electrons intrinsically
offers anisotropic spin interactions as required by Kitaev model. We have grown
the crystals of YbOCl and synthesized the polycrystals of SmSI, ErOF, HoOF and
DyOF, and made careful structural characterizations. We carry out magnetic and
heat capacity measurements down to 1.8 K and find no obvious magnetic
transition in all the samples but DyOF. The van der Waals interlayer coupling
highlights the true two-dimensionality of the family which is vital for the
exact realization of Abelian/non-Abelian anyons, and the graphene-like feature
will be a prominent advantage for developing miniaturized devices. The family
is expected to act as an inspiring material platform for the exploration of KSL
physics.

Strongly Correlated Electrons;Materials Science;Superconductivity