Quantum geometry in the dynamics of band-projected operators

Abstract

We study the dynamics of electrons in crystalline solids in the presence of inhomogeneous external electric and magnetic fields. We present a manifestly gauge-invariant operator-based approach without relying on a semiclassical wavepacket construction, and derive the field-induced corrections to the equations of motion at the operator level. This includes the Berry curvature induced anomalous velocity and contributions arising from the quantum geometry of the Bloch bands. We show explicitly how these multi-band effects are manifested in an effective single band approximation. We present a formalism that allows for a systematic expansion to an arbitrary order in the inhomogeneity of the applied fields, as well as a way to compute the matrix elements in Bloch basis.