Odd-parity quadrupole order and induced nonreciprocal transport in the kagome metal CsTi$_3$Bi$_5$ driven by quantum interference

TL;DR

This paper predicts an odd-parity bond order in CsTi$_3$Bi$_5$ kagome metal driven by quantum interference, leading to nonreciprocal transport phenomena and nematic Fermi surface deformation, supported by experimental consistency.

Contribution

It introduces a novel odd-parity bond order mechanism in kagome metals induced by quantum interference among spin fluctuations, a concept not previously explored in this context.

Findings

Prediction of E1u odd-parity bond order in CsTi$_3$Bi$_5$

Observation of nematic Fermi surface deformation (~1%)

Induction of non-linear Hall effect and emergent electromagnetism

Abstract

Kagome metals present a fascinating platform of quantum phases thanks to the interplay between the geometric frustration and strong electron correlation. Here, we propose the emergence of the electric odd-parity bond order (BO) that originates from the intra-unit-cell odd-parity configuration in recently discovered kagome metal CsTi$_3$Bi$_5$. The predicted E1u BO is induced by the beyond-mean-field mechanism, that is, the quantum interference among different sublattice spin fluctuations. Importantly, the accompanied nematic deformation of the Fermi surface is just ~1% while the intensity of the quasiparticle interference signal exhibits drastic nematic anisotropy, consistent with the scanning tunneling microscope measurements in CsTi$_3$Bi$_5$. The present odd-parity BO triggers interesting phenomena, such as the non-linear Hall effect and emergent electromagnetism.