Spin Transport and Accumulation in 2D Weyl Fermion System

TL;DR

This paper investigates spin transport phenomena in a 2D Weyl fermion system, revealing how impurity scattering influences the spin Hall effect and how it can be tuned via Fermi energy or impurity size.

Contribution

It provides a theoretical analysis of spin Hall effect mechanisms in 2D Weyl systems, highlighting impurity-induced skew scattering and potential tunability of the spin Hall angle.

Findings

Spin Hall angle has a fixed sign and depends strongly on impurity parameters.

Spin transport is driven by spin-torque current in the system.

The spin Hall effect can be tuned by adjusting Fermi energy or impurity size.

Abstract

In this work, we study the spin Hall effect and Rashba-Edelstein effect of a 2D Weyl fermion system in the clean limit using the Kubo formalism. Spin transport is solely due to the spin-torque current in this strongly spin-orbit coupled (SOC) system, and chiral spin-flip scattering off non-SOC scalar impurities, with potential strength $V$ and size $a$, gives rise to a skew-scattering mechanism for the spin Hall effect. The key result is that the resultant spin-Hall angle has a fixed sign, with $\theta^{SH} \sim O \left(\tfrac{V^2}{v_F^2/a^2} (k_F a)^4 \right)$ being a strongly-dependent function of $k_F a$, with $k_F$ and $v_F$ being the Fermi wave-vector and Fermi velocity respectively. This, therefore, allows for the possibility of tuning the SHE by adjusting the Fermi energy or impurity size.