Tri-Hexagonal charge order in kagome metal CsV$_{3}$Sb$_{5}$ revealed by $^{121}$Sb NQR

TL;DR

This study uses $^{121}$Sb NQR to reveal a Tri-Hexagonal charge order in the kagome superconductor CsV$_3$Sb$_5$, showing a first order CDW transition and coexistence with superconductivity.

Contribution

It provides the first direct NQR evidence of Tri-Hexagonal charge order and detailed characterization of the CDW transition in CsV$_3$Sb$_5$.

Findings

Charge density wave transition at 94 K with a first order nature.

Tri-Hexagonal deformation of the CDW order with superlattice modulation.

Superconductivity coexists with the CDW phase and exhibits conventional s-wave behavior.

Abstract

We report $^{121}$Sb nuclear quadrupole resonance (NQR) measurements on kagome superconductor CsV$_3$Sb$_5$ with $T_{\rm c}=2.5$ 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.