Odd-parity bond order and induced nonreciprocal transport in the kagome metal CsTi3Bi5 driven by quantum interference

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 CsTi3Bi5. 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 CsTi3Bi5. The present odd-parity BO triggers interesting phenomena, such as the nonlinear Hall effect and emergent electromagnetism.