Microscopic origin of period-four stripe charge-density-wave in kagome metal CsV$_3$Sb$_5$

TL;DR

This study proposes a microscopic mechanism for the period-four stripe charge-density-wave in kagome metal CsV$_3$Sb$_5$, linking Fermi surface nesting and magnetic fluctuations to the observed CDW pattern.

Contribution

It introduces a theoretical explanation for the microscopic origin of the experimentally observed stripe CDW in kagome superconductors, focusing on Fermi surface nesting and magnetic fluctuations.

Findings

The reconstructed Fermi surface's nesting vector induces a 4a_0 period CDW.

The stripe CDW involves both hopping integral modulations and on-site potentials.

The theoretical pattern aligns qualitatively with experimental observations.

Abstract

The interplay between unconventional density waves and exotic superconductivity has attracted growing interest. Kagome superconductors $A\rm{V}_3\rm{Sb}_5$ ($A = \rm{K}, \rm{Rb}, \rm{Cs}$) offer a platform for studying quantum phase transitions and the resulting symmetry breaking. Among these quantum phases, the $4a_0$ stripe charge-density-wave (CDW) has been widely observed for $A=\rm{Rb}$ and $\rm{Cs}$ by scanning tunneling microscopy (STM) and nuclear magnetic resonance (NMR) measurements. However, the microscopic origin of the $4a_0$ stripe CDW remains elusive, and no theoretical studies addressing this phenomenon have been reported so far. In this paper, we propose a microscopic mechanism for the emergence of the $4a_0$ stripe CDW. We analyze the CDW instability in the 12-site kagome lattice Hubbard model with the $2\times2$ bond order driven by the paramagnon-interference mechanism by focusing on the short-range magnetic fluctuations due to the geometrical frustration of kagome lattice. We reveal that the nesting vector of the reconstructed Fermi surface, formed by the $2\times 2$ bond order, gives rise to a $4a_0$-period CDW. Remarkably, the obtained stripe CDW is composed of both the off-site hopping integral modulations and on-site potentials. The real-space structure of the stripe CDW obtained here is in good qualitative agreement with the experimentally observed stripe pattern.