Inverse Spin Hall Effect in Nonequilibrium Dirac Systems Induced by Anomalous Flow Imbalance

TL;DR

This paper investigates how space-dependent chiral gauge fields and thermodynamic gradients in Dirac fermions induce an inverse spin Hall effect, revealing robust surface states and specific charge currents linked to experimental observations.

Contribution

It introduces a novel mechanism connecting chiral gauge fields and thermodynamic gradients to the inverse spin Hall effect in Dirac systems, emphasizing the role of noncollinear magnetic fields.

Findings

Surface Fermi arc and chiral Landau level states are robust against impurities.

Charge currents depend on chemical potential and temperature gradients, matching experimental data.

Proper treatment of ultraviolet cutoff is crucial for lattice calculations.

Abstract

We study Dirac fermions in the presence of a space-dependent chiral gauge field and thermodynamic gradients, establishing a connection to the inverse spin Hall effect. The chiral gauge field induces a chiral magnetic field, resulting in a surface Fermi arc state and a chiral Landau level state which, although is delocalized in the bulk, we show to be more robust against impurities. By applying chemical potential and temperature gradients, we achieve nonzero charge currents, with each gradient leading to distinct Fermi level dependencies, both of which have been observed in a recent experiment. Unlike the conventional mixed axial-gravitational anomaly, our currents require a noncollinear chiral magnetic field and thermodynamic gradient. We further derive low-energy transport formulas and demonstrate the importance of carefully treating the ultraviolet cutoff for understanding our lattice calculations.