Quantum-metric-induced giant and reversible nonreciprocal transport phenomena in chiral loop-current phases of kagome metals

TL;DR

This paper uncovers how quantum geometric properties in kagome metals lead to giant, reversible nonreciprocal electrical transport phenomena, driven by loop-current order and quantum metric effects, revealing new insights into symmetry-breaking states.

Contribution

It demonstrates that quantum metric effects significantly enhance nonreciprocal transport in kagome metals with loop-current order, providing a theoretical framework for understanding giant eMChA phenomena.

Findings

Giant and reversible eMChA coefficient proportional to orbital magnetization and electron lifetime.

Quantum metric effects dramatically enhance eMChA by approximately 100 times.

Loop-current order induces non-centrosymmetric states, enabling nonreciprocal transport.

Abstract

Rich spontaneous symmetry-breaking phenomena with nontrivial quantum geometric properties in metals represent central issues in condensed matter physics. In this context, the emergence of chiral loop-current order, accompanied by time-reversal symmetry-symmetry breaking in various kagome metals, has garnered significant attention. Particularly noteworthy is the giant electrical magnetochiral anisotropy (eMChA) in CsV3Sb5, which provides compelling evidence of time-reversal-symmetry and inversion-symmetry breakings. However, the underlying essence of this observation has remained obscured due to the lack of theoretical understanding. Here, we reveal that the loop-current order causes giant and reversible eMChA coefficient, $\gamma_{eM}$, is proportional to the loop-current-induced orbital magnetization $M_{orb}$ times the lifetime of conduction electrons $\tau$. In kagome metals, the derived $\gamma_{eM}$ is substantial and reversible by minute magnetic fields, due to the large $\tau (\gg a_0/v_{Fermi})$ and the field-induced reversal of $M_{orb}$. By considering the experimentally observed stripe charge-density wave, the loop-current state becomes non-centrosymmetric, thereby giving rise to the eMChA. Surprisingly, the quantum-metric, which defines a fundamental geometric aspect of Bloch wavefunctions, acquires significant momentum dependence in the loop-current phase, resulting in a dramatic enhancement of eMChA by $\sim100$ times. This research not only clarifies the fundamental symmetry-breaking states in kagome metals, but also opens a new path for exploring quantum-metric-induced phenomena arising from exotic quantum phase transitions in strongly correlated metals