Geometry-Driven Nonlinear Orbital Magnetoelectric Effect

TL;DR

This paper introduces a nonlinear orbital magnetoelectric effect in centrosymmetric materials, deriving a gauge-invariant theory that distinguishes intrinsic and extrinsic contributions, and suggests it can be experimentally observed via Kerr measurements.

Contribution

It proposes and theoretically formulates a quadratic orbital magnetoelectric effect in centrosymmetric materials, expanding the potential materials for observation.

Findings

Nonlinear response is less constrained by symmetries in 2D systems.

The effect's magnitude is within current Kerr measurement sensitivity.

The theory separates intrinsic and extrinsic contributions with distinct relaxation time dependencies.

Abstract

We propose a nonlinear orbital magnetoelectric effect, which generates orbital magnetization quadratically in centrosymmetric materials where the linear orbital magnetoelectric effect is strictly forbidden. Using extended semiclassical formulation, we derive a gauge-invariant microscopic theory that separates intrinsic and extrinsic contributions and establishes their distinct dependence on the relaxation time, providing an experimental discriminator. In two-dimensional systems the nonlinear response is far less constrained by out-of-plane rotational symmetries than the linear orbital magnetoelectric effect, substantially enlarging the materials platform. Microscopically, the dominant contributions are governed by a Hermitian-connection structure. Finally, we estimate that the magnitude of the nonlinear orbital magnetoelectric effect lies within the sensitivity of state-of-the-art magneto-optical Kerr measurements.