Strain-induced nonlinear spin Hall effect in topological Dirac semimetal

TL;DR

This paper predicts a strain-induced nonlinear spin Hall effect in topological Dirac semimetals, enabling efficient, tunable generation of spin currents via an applied electric field.

Contribution

It introduces a novel nonlinear spin Hall effect driven by strain as an effective axial magnetic field in Dirac semimetals, analyzed through chiral kinetic theory.

Findings

Nonlinear spin Hall current is quadratic in electric field.

The effect can generate fully spin-polarized, rectified spin currents.

The spin current magnitude can be tuned by gate voltage and strain.

Abstract

We show that an electric field applied to a strained topological Dirac semimetal, such as Na3Bi and Cd3As2, induces a spin Hall current that is quadratic in the electric field. By regarding the strain as an effective "axial magnetic field" for the Dirac electrons, we investigate the electron and spin transport semiclassically in terms of the chiral kinetic theory. The nonlinear spin Hall effect arises as the cross effect between the regular Hall effect driven by the axial magnetic field and the anomalous Hall effect coming from the momentum-space topology. It provides an efficient way to generate a fully spin-polarized and rectified spin current out of an alternating electric field, which is sufficiently large and can be directly tuned by the gate voltage and the strain.