Quantum Metric-induced Oscillations in Flat Bands

TL;DR

This paper introduces a novel oscillation mechanism driven by the interband quantum metric, which influences electron dynamics in flat bands and can produce significant drift currents under strong electric fields.

Contribution

It reveals quantum metric induced oscillations as a new mechanism affecting electron transport, even in dispersionless flat bands, expanding understanding of electron dynamics under strong fields.

Findings

Quantum metric induced oscillations persist in flat bands.

QMO can generate drift currents comparable to Bloch oscillations.

QMO drift current increases linearly with electric field.

Abstract

The transport of Bloch electrons under strong fields is traditionally understood through two mechanisms: intraband Bloch oscillations and interband Zener tunneling. Here, we propose an oscillation mechanism induced by the interband quantum metric, which would significantly affect the electron dynamics under strong fields. By considering the multiband dynamics to the second order of the density matrix, we reveal that quantum metric induced oscillations (QMOs) persist regardless of band dispersion, even in exactly dispersionless flat bands. The resultant drift current can reach a magnitude comparable to the Bloch oscillation induced drift current in systems where interband tunneling is negligible. Notably, the QMO induced drift current increases linearly with electric field strength under the constraints of time-reversal or spatial-inversion symmetry, emerging as the primary delocalized current. We further show that both one-dimensional and two-dimensional superlattices are potential platforms for investigating QMO.