Microscopic insights into the pseudo gap phase of CsV₃Sb₅

The layered compounds AV₃Sb₅ (A = K, Rb, and Cs) with a vanadium kagome lattice exhibit various interesting electronic phases, such as superconductivity [1] and a 2x2 charge density wave (CDW) [2]. Most notably, CsV₃Sb₅ was found to exhibit a time-reversal symmetry (TRS) broken state without the presence of local magnetic moments [3]. A chiral flux phase that arises within the 2x2 CDW state has been proposed as a possible TRS breaking mechanism. Direct experimental evidence for the chiral flux phase would be desirable to better understand the rich phenomenology of quantum states in these kagome compounds.

We present results from cryogenic scanning tunneling microscopy experiments on cleaved bulk crystals of CsV₃Sb₅. The goal of our study is to shed light on the pseudo gap phase that appears in the low energy local density of states of the 2x2 CDW state. To this end, we combine high-resolution spectroscopy and quasiparticle interference with scattering experiments in which we study the response of the pseudo gap phase to atomic scale perturbations. We compare our observations with results from microscopic model calculations with the focus on the spectral features of the chiral flux phase.

[1]B.R. Ortiz et al., Rev. Mater. 3 094407 (2019)

[2]H. Zhao et al., Nature 599, 216-221 (2021)

[3]C. Guo et. al., Nature 611, 461-466 (2022)