Necessity of Time-Reversal Symmetry Breaking for the Polar Kerr Effect in Linear Response

TL;DR

This paper demonstrates that the polar Kerr effect in linear response is absent in systems respecting time-reversal symmetry, due to Onsager symmetry of the electromagnetic response, especially in backscattering geometries.

Contribution

It provides a theoretical proof linking the absence of Kerr effect to time-reversal symmetry and Onsager symmetry in the electromagnetic response.

Findings

Kerr effect vanishes if Onsager symmetry is preserved.

Reflectivity tensor expressed via retarded Green's function.

Backscattering geometry is crucial for the analysis.

Abstract

We show that, measured in a backscattering geometry, the polar Kerr effect is absent if the nonlocal electromagnetic response function respects Onsager symmetry, characteristic of thermodynamic states that preserve time-reversal symmetry. A key element is an expression for the reflectivity tensor in terms of the retarded Green's function.