Quantum geometry and dipolar dynamics in the orbital magneto-electric effect

TL;DR

This paper explores how quantum geometry, specifically the quantum metric, influences the orbital magneto-electric effect in tilted Dirac fermions, proposing quantum metric engineering to enhance orbital torques.

Contribution

It reveals the role of nonequilibrium dipole moments related to the quantum metric in the orbital magneto-electric effect, especially in insulating tilted Dirac fermions.

Findings

Dipole moments proportional to the quantum metric contribute to the OME.

Intrinsic and extrinsic OMEs depend on electric field orientation.

Quantum metric engineering can maximize orbital torques.

Abstract

We show that the orbital magneto-electric effect (OME) -- the generation of a steady-state orbital angular momentum density -- is partly the result of a nonequilibrium dipole moment generated via Zitterbewegung and proportional to the quantum metric. For tilted massive Dirac fermions this dipole gives the only contribution to the OME in the insulating case, while the intrinsic and extrinsic OMEs occur for different electric field orientations, yielding an experimental detection method. Our results suggest quantum metric engineering as a route towards maximizing orbital torques.