Optical gyrotropy from axion electrodynamics in momentum space

TL;DR

This paper explores how axion electrodynamics in momentum space influences optical gyrotropy and surface conductance in solids, revealing fundamental constraints and microscopic mechanisms beyond traditional symmetry considerations.

Contribution

It introduces a unified theory linking Berry-phase effects to optical gyrotropy and surface conductance, highlighting the role of momentum-space axion electrodynamics in these phenomena.

Findings

Optical rotatory power along crystal axes sums to zero, matching experimental data.

Berry-phase mechanism explains surface conductance at gyrotropic interfaces.

The theory extends understanding of gauge field analogues in electronic momentum space.

Abstract

Several emergent phenomena and phases in solids arise from configurations of the electronic Berry phase in momentum space that are similar to gauge field configurations in real space such as magnetic monopoles. We show that the momentum-space analogue of the "axion electrodynamics" term $\mathbf{E}\cdot\mathbf{B}$ plays a fundamental role in a unified theory of Berry-phase contributions to optical gyrotropy in time-reversal invariant materials and the chiral magnetic effect. The Berry-phase mechanism predicts that the rotatory power along the optic axes of a crystal must sum to zero, a constraint beyond that stipulated by point group symmetry, but observed to high accuracy in classic experimental observations on $\alpha$-quartz. Furthermore, the Berry mechanism provides a microscopic basis for the surface conductance at the interface between gyrotropic and nongyrotropic media.