Quantum Metric-induced Oscillations in Flat Bands

The transport of Bloch electrons under strong fields is traditionally understood through two mechanisms: intraband Bloch oscillations and interband Zener tunneling. Here we propose a new 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 (QMO) persist regardless of band dispersion, even in exactly flat bands. The resultant drift current can reach a magnitude comparable to the Bloch oscillations-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.