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

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.