Non-Hermitian linear electro-optic effect in three-dimensional materials
Tiago A. Morgado, Tatiana G. Rappoport, Stepan S. Tsirkin, Sylvain Lannebère, Ivo Souza, Mário G. Silveirinha
Abstract
Here, we present an in-depth theoretical analysis of the linear electro-optic effect in low-symmetry three-dimensional (3D) conductive materials with large Berry curvature dipoles. Our study identifies two distinct kinetic contributions to the linear electro-optic effect: a gyrotropic Hermitian (conservative) piece and a non-Hermitian term that can originate optical gain. We concentrate on the study of 3D materials belonging to the 32 (${D}_{3}$) point group subject to a static electric bias along the trigonal axis. Our investigation shows that doped trigonal tellurium has promising properties, with its gyrotropic electro-optic response offering the potential for realizing electrically biased electromagnetic isolators and inducing significant optical dichroism. Most notably, it is demonstrated that under sufficiently large static electric bias, tellurium's non-Hermitian electro-optic response may lead to optical gain. Using first-principles calculations, it is shown that $n$-doped tellurium is particularly promising, as it can host significantly larger Berry curvature dipoles than the more common $p$-doped tellurium.