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

Abstract

Emergence of quantum orders with nontrivial quantum geometric properties in metals represent central issues in condensed matter physics. In this context, recently discovered chiral loop-current order in kagome metals has garnered significant attention. Particularly noteworthy is the giant electrical magnetochiral anisotropy (eMChA) observed in CsV₃Sb₅, which provides compelling evidence for the simultaneous breaking of time-reversal and inversion symmetries. However, the origin of the eMChA and its fundamental connection to the loop-current remain highly elusive, as the loop-current itself preserves inversion symmetry. Here, we demonstrate that the loop-current phase breaks inversion symmetry in the presence of the experimentally observed stripe charge-density wave, leading to finite eMChA coefficient [Formula: see text]. In this mechanism, [Formula: see text] is proportional to the product of the loop-current-induced orbital magnetization, [Formula: see text], and the lifetime of conduction electrons, <i>τ</i>. Therefore, [Formula: see text] is reversible by the magnetic fields, and it takes large value in kagome metals with [Formula: see text] (=lattice constant). 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 ∼100 times. This research not only clarifies the fundamental symmetry-breaking states in kagome metals but also opens a path for exploring quantum metric-induced phenomena arising from exotic quantum phase transitions in various metals.