Quantum Fluctuation of the Quantum Geometric Tensor and its Manifestation as Intrinsic Hall Signatures in Time-Reversal Invariant Systems

TL;DR

This paper investigates intrinsic thermal Hall noise signatures in time-reversal invariant systems, revealing quantum fluctuations of the quantum geometric tensor as measurable indicators of band geometric properties.

Contribution

It uncovers intrinsic thermal Hall noise contributions linked to quantum geometric tensor fluctuations, expanding understanding of Hall effects beyond extrinsic mechanisms.

Findings

Intrinsic thermal Hall noise exists in linear and nonlinear regimes.

Second-order thermal Hall noise includes intrinsic and extrinsic parts.

Intrinsic noise directly relates to quantum geometric tensor fluctuations.

Abstract

In time-reversal invariant systems, all charge Hall effects predicted so far are extrinsic effects due to the dependence on the relaxation time. We explore intrinsic Hall signatures by studying quantum noise spectrum of the Hall current in time-reversal invariant systems, and discover intrinsic thermal Hall noises in both linear and nonlinear regimes. As the band geometric characteristics, quantum geometric tensor and Berry curvature play critical roles in various Hall effects, so are their quantum fluctuations. It is found that the thermal Hall noise in linear order of the electric field is purely intrinsic, and the second-order thermal Hall noise has both intrinsic and extrinsic contributions. In particular, the intrinsic part of the second-order thermal Hall noise is a manifestation of the quantum fluctuation of quantum geometric tensor, which widely exists as long as Berry curvature is nonzero. These intrinsic thermal Hall noises provide direct measurable means to band geometric information, including Berry curvature related quantities and quantum fluctuation of quantum geometric tensor.