Geometry-Enhanced Second-Harmonic Charge Transport in Kagome Superconductor CsV₃Sb₅.

Abstract

The inherent nontrivial band topology and geometric frustration in layered kagome materials enable rich correlated states such as charge density wave (CDW) and superconductivity. Recent scanning tunneling microscopy and transport studies of CsV₃Sb₅ suggest chirality in these states. To explore this further, we performed second-harmonic measurements with a nonuniform current flow. Distinct nonreciprocal signals emerged in the CDW state, akin to the phenomena observed in magnetic topological insulators with chiral edge states. Although these signals are strongly affected by the Nernst effect, the residual second-harmonic signals identified after subtraction of thermoelectric contributions points to the chiral scattering process under the nonuniform current density. These findings underscore the importance of geometry design in the second-harmonic generation within two-dimensional devices and highlight its critical role in the observation of chiral phenomena in such materials.