# Complete optical valley polarization in Weyl semimetals in strong magnetic fields

## TL;DR

This paper develops a theory showing that strong magnetic fields can induce complete optical valley polarization in Weyl semimetals by exploiting symmetry breaking and interband transitions, with potential experimental signatures.

## Contribution

It introduces a theoretical framework for achieving complete optical valley polarization in Weyl semimetals under strong magnetic fields, highlighting control via magnetic field and light direction.

## Key findings

- Complete valley polarization can reach 100% in certain frequency ranges.
- Interband Landau level transitions serve as signatures of valley polarization.
- The theory applies to materials like TaAs, suggesting experimental observability.

## Abstract

We present a theory of an optically induced valley polarization in an interacting, time-reversal symmetric Weyl semimetal placed under strong magnetic fields. Because the application of a magnetic field reduces the symmetry of the crystal, the optical absorption intensity differs at Weyl nodes that were equivalent by symmetry at zero field. At strong magnetic field, the difference in the absorption intensity reaches 100% for a sizeable frequency interval of the incident light. This complete valley polarization originates from interband transitions involving the chiral Landau level, and can be controlled by changing the directions of the magnetic field and the light propagation. We identify the splitting of $0\to 1$ or $-1\to 0$ inter Landau level transitions as an observable signature of the complete valley polarization, and discuss its manifestation in the TaAs family of materials.