Symmetry Analysis of the Non-Hermitian Electro-Optic Effect in Crystals

TL;DR

This paper explores how crystal symmetry influences the non-Hermitian electro-optic effect, revealing symmetry-dependent optical gain and dissipation, with implications for designing polarization-sensitive optical devices using Weyl semimetals.

Contribution

It provides a symmetry-based analysis of the non-Hermitian electro-optic effect, identifying how point group symmetries enable polarization-dependent optical gain without gyrotropy.

Findings

Symmetry determines whether gain or dissipation occurs for specific polarizations.

Weyl semimetals can exhibit significant non-Hermitian electro-optic effects.

Optical gain and attenuation can be controlled via symmetry and external bias.

Abstract

Here, we investigate how crystal symmetry tailors the non-Hermitian electro-optic effect arising from the Berry curvature dipole. Specifically, we demonstrate the critical influence of the material's point group symmetry and external electric biases in shaping this effect, leading to current-induced optical gain and non-reciprocal optical responses. Through a symmetry-based analysis of the crystallographic point groups, we identify how different symmetries affect the electro-optic response, enabling the engineering of polarization-dependent optical gain without the need for gyrotropic effects. In particular, we demonstrate that the non-Hermitian electro-optic response in a broad class of crystals is characterized by linear dichroic gain. In this type of response, the eigenpolarizations that activate the gain or dissipation are linearly polarized. Depending on the point group symmetry, it is possible to achieve gain (or dissipation) for all eigenpolarizations or to observe polarization-dependent gain and dissipation. Weyl semimetals emerge as promising candidates for realizing significant non-Hermitian electro-optic effects and linear dichroic gain. We further examine practical applications by studying the reflectance of biased materials in setups involving mirrors, demonstrating how optical gain and attenuation can be controlled via symmetry and bias configurations.