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.
Highlights
The idea of spin current, which first emerged about 50 years ago[1,2], has significantly developed the field of nanoscale condensed matter physics, in particular of spintronics[3,4,5]
The intrinsic spin Hall conductivity is determined by the separation of the DPs in momentum space[22,23,24,25], which is analogous to the anomalous Hall effect (AHE) in a Weyl semimetal (WSM) with broken time-reversal symmetry (TRS)[26,27]
In order to tune and enhance the spin Hall current from its fixed value in topological Dirac semimetals (TDSMs), we need to go beyond the linear response regime with respect to the electric field, which is necessary in making use of TDSM as an efficient spin current injector
Summary
The idea of spin current, which first emerged about 50 years ago[1,2], has significantly developed the field of nanoscale condensed matter physics, in particular of spintronics[3,4,5]. The intrinsic spin Hall conductivity is determined by the separation of the DPs in momentum space[22,23,24,25], which is analogous to the anomalous Hall effect (AHE) in a Weyl semimetal (WSM) with broken time-reversal symmetry (TRS)[26,27]. In order to tune and enhance the spin Hall current from its fixed value in TDSM, we need to go beyond the linear response regime with respect to the electric field, which is necessary in making use of TDSM as an efficient spin current injector. The nonlinear transport is important from the topological point of view; a recent study has shown that the momentum-space Berry curvature gives rise to the nonlinear Hall transport[30]. The distribution is shifted from the equilibrium distribution (dashed circle) transverse as well as longitudinal to E at linear response (red solid circle), due to the regular Hall effect (RHE) under B5. (small grey arrows), which leads to the anomalous velocity
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