Sliding ferroelectricity tunable conventional and anomalous spin Hall effects in bilayer 1T'-WTe2

Abstract: The spin Hall effect, recognized for its high-speed, low-power, and highly controllable characteristics, is a key enabler for next-generation memory and logic devices. However, a primary challenge lies in achieving 180$^{\circ}$ magnetization switching without an external magnetic field in spin-orbit torque devices. Here, we propose a method to tune the conventional and anomalous spin Hall effects by the intrinsic sliding ferroelectricity. Importantly, the anomalous spin Hall effect can enable the field-free switching of perpendicular magnetization. We find a substantial anomalous spin Hall conductivity of $σ{xy}^{y}$ = 45.62 ($\hbar$/e)S/cm and $σ{yx}^{y}$ = 56.84 ($\hbar$/e)S/cm in monolayer 1T'-WTe$2$. These values are significantly enhanced to $σ{xy}^{y}$ = -96.77 ($\hbar$/e)S/cm and $σ_{yx}^{y}$ = 104.03 ($\hbar$/e)S/cm in the bilayer 1T'-WTe$_2$. More interestingly, the sliding ferroelectricity enables reversible switching of the signs and magnitudes for both the conventional and anomalous spin Hall conductivities. This originates from the fact that the sliding ferroelectric markedly shifts the relative spin Berry curvature contributions from the valence and conduction bands around the $Γ$-X path. Our findings not only reveal a strong coupling between sliding ferroelectricity and spin transport, but also propose a strategy for the nonvolatile electrical control of spintronic devices.