Measurement of interaction-dressed Berry curvature and quantum metric in solids by optical absorption

TL;DR

This paper introduces a method to measure interaction-influenced Berry curvature and quantum metric in solids using optical absorption, accounting for many-body effects at finite temperature.

Contribution

It generalizes quantum geometric concepts to interacting systems and proposes a measurement approach via charge polarization susceptibility from optical absorption spectra.

Findings

Quantum geometric properties are robust against interactions in gapped systems.

Spectral functions from optical absorption can reveal dressed Berry curvature and quantum metric.

Results suggest protection of quantum geometry by energy gaps in Chern insulators.

Abstract

The quantum geometric properties of a Bloch state in momentum space are usually described by the Berry curvature and quantum metric. In realistic gapped materials where interactions and disorder render the Bloch state not a viable starting point, we generalize these concepts by introducing dressed Berry curvature and quantum metric at finite temperature, in which the effect of many-body interactions can be included perturbatively. These quantities are extracted from the charge polarization susceptibility caused by linearly or circularly polarized electric fields, whose spectral functions can be measured from momentum-resolved exciton or infrared absorption rate. As a concrete example, we investigate Chern insulators in the presence of impurity scattering, whose results suggest that the quantum geometric properties are protected by the energy gap against many-body interactions.