Quantum Geometric Oscillations in Two-Dimensional Flat-Band Solids

TL;DR

This paper explores quantum geometric oscillations in 2D flat-band solids, revealing how Berry curvature induces unique electron trajectories under electric fields, distinct from traditional Bloch oscillations.

Contribution

It introduces the concept of quantum geometric oscillations driven by Berry curvature in flat-band 2D materials, highlighting their distinct properties from Bloch oscillations.

Findings

Geometric oscillations are driven by Berry curvature in flat-band systems.

Oscillation size saturates at a nonzero value in strong fields.

Oscillations exhibit even symmetry under field inversion, unlike Bloch oscillations.

Abstract

Two-dimensional van der Waals heterostructures can be engineered into artificial superlattices that host flat bands with significant Berry curvature and provide a favorable environment for the emergence of novel electron dynamics. In particular, the Berry curvature can induce an oscillating trajectory of an electron wave packet transverse to an applied static electric field. Though analogous to Bloch oscillations, this novel oscillatory behavior is driven entirely by quantum geometry in momentum space instead of band dispersion. While the orbits of Bloch oscillations can be localized by increasing field strength, the size of the geometric orbits saturates to a nonzero plateau in the strong-field limit. In non-magnetic materials, the geometric oscillations are even under inversion of the applied field, whereas the Bloch oscillations are odd, a property that can be used to distinguish these two co-existing effects.