Breaking of time-reversal and inversion symmetry in kagome metals AV₃Sb₅

Recently, various symmetry breaking in kagome metals AV₃Sb₅ have been reported in the regions where both itinerancy and localization are important. Typical examples are "bond order[1]" with modulation of the hopping δt, and "charge loop current[2]," which accompanies a permanent circular current. While the existence of a lot of experimental reports, the fundamental question of "why these non-local orders are stable?" remains unresolved. Conventional mean-field theories, required the unrealistically large long-range interactions to explain these phenomena. To overcome this difficulty, we develop the many body theory with vertex corrections and found that the non-local orders emerge due to the bond fluctuations [3].

More recently, the inversion symmetry breaking (ISB) at low temperatures has also been reported, and there is a desire to elucidate its origin and relationship with other phases. We found that both ISB and time-reversal symmetry breaking by charge loop current induce interesting phenomena such as non-reciprocal transport. In the presentation, I would like to discuss a wide topic on kagome metals as well as our recent progress.