Symmetry Conditions for Non-reciprocal Light Propagation in Magnetic Crystals

TL;DR

This paper uses symmetry analysis to identify magnetic crystal groups capable of exhibiting non-reciprocal light propagation and predicts new types of directional optical anisotropies beyond known effects.

Contribution

It provides a comprehensive symmetry-based classification of magnetic point groups that can host non-reciprocal optical phenomena and predicts new anisotropic effects in these materials.

Findings

Identified magnetic point groups enabling directional anisotropies.

Listed candidate materials for observing non-reciprocal light propagation.

Predicted new types of directional optical anisotropies.

Abstract

Recent studies demonstrated the violation of reciprocity in optical processes in low-symmetry magnetic crystals. In these crystals the speed of light can be different for counter-propagating beams. Correspondingly, they can show strong directional anisotropies such as direction dependent absorption also called directional dichroism[S. Bord\'acs et al., Nat. Phys. 8, 734 (2012); M. Saito et al., J. Phys. Soc. Jpn. 77, 013705 (2008)]. Based on symmetry considerations, we identify the magnetic point groups of materials which can host such directional anisotropies and also provide a list of possible candidate materials to observe these phenomena. In most of these cases, the symmetry of the crystal allows directional anisotropy not only for optical processes but also for the propagation of beams of particles and scalar waves. We also predict new types of directional optical anisotropies -- besides the optical magnetoelectric effect and the magnetochiral dichroism investigated so far -- and specify the magnetic point groups of crystals where they can emerge.