Chiral Anomalies through Laser-Induced Chiral Gauge Fields in Disordered 3D Dirac Semimetals

Inspired by a recent experiment that observed a significant photoexcited surface current in bismuth semimetal, we consider a Dirac semimetal subjected to a gradient chiral gauge field. The chiral gauge field, which can be generated for instance by circularly polarized light (CPL), is known to separate a Dirac fermion into a Weyl pair, leading to an appearance of Fermi arc states. Our study reveals that, due to the gradient, which can be achieved through the skin effect of the CPL on the semimental surface, one of the Fermi arc states leaks into the bulk, becoming a delocalized chiral Landau level state. We then introduce a homogeneous disorder and find that remarkably the chiral Landau level state exhibits greater robustness against scattering than the Fermi arc state, resulting in distinct lifetimes for two chiral states. Exploiting this asymmetry, we demonstrate an emergence of finite anomalous current, all without applications of external electric and magnetic fields. This discovery also serves as a realization of non-Hermitian topological quantum field theory within materials.