Chiral light amplifier with pumped Weyl semimetals

TL;DR

This paper demonstrates that pumped Weyl semimetals can exhibit a chiral magnetic instability leading to anomalous surface reflectance exceeding unity for circularly polarized light, revealing new electromagnetic properties.

Contribution

It introduces the concept of a chiral magnetic instability in pumped Weyl semimetals and links it to observable anomalous reflectance phenomena.

Findings

Reflectance exceeds unity for certain frequencies and polarizations.

Chiral magnetic instability causes anomalous electromagnetic behavior.

Surface reflectance depends on electric, chiral magnetic, and Hall conductivities.

Abstract

Parallel electric and magnetic fields applied to Weyl semimetals pump axial charge via the axial anomaly until balanced by intervalley relaxation. The resulting nonequilibrium steady state exhibits the chiral magnetic effect as well as the anomalous Hall effect, which coupled with Maxwell's equations leads to unstable electromagnetic waves at low frequency and long wavelength. Here, we show that such chiral magnetic instability manifests itself as anomalous reflectance of the surface of pumped Weyl semimetal. Depending on electric, chiral magnetic, and anomalous Hall conductivities, the reflectance is found to exceed unity in a finite range of frequency for a circularly polarized light incident along the direction of Weyl node separation.