Tri-Hexagonal charge order in kagome metal CsV${}_3$Sb${}_5$ revealed by ${}^{121}$Sb NQR

Abstract

We report ${}^{121}$Sb nuclear quadrupole resonance (NQR) measurements on kagome superconductor CsV${}_3$Sb${}_5$ with $T_{\mathrm{c}}=2.5$ K. ${}^{121}$Sb NQR spectra split after a charge density wave (CDW) transition at $94$ K, which demonstrates a commensurate CDW state. The coexistence of the high temperature phase and the CDW phase between $91$ K and $94$ K manifests that it is a first order phase transition. The CDW order exhibits Tri-Hexagonal deformation with a lateral shift between the adjacent kagome layers, which is consistent with $2\times 2\times 2$ superlattice modulation. The superconducting state coexists with CDW order and shows a conventional s-wave behavior in the bulk state.