Intrinsic spin Hall torque in a moire Chern magnet
In spin torque magnetic memories, electrically actuated spin currents are used to switch a magnetic bit. Typically, these require a multilayer geometry including both a free ferromagnetic layer and a second layer providing spin injection. For example, spin may be injected by a nonmagnetic layer exhibiting a large spin Hall effect, a phenomenon known as spin-orbit torque. Here, we demonstrate a spin-orbit torque magnetic bit in a single two-dimensional system with intrinsic magnetism and strong Berry curvature. We study AB-stacked MoTe2/WSe2, which hosts a magnetic Chern insulator at a carrier density of one hole per moire superlattice site. We observe hysteretic switching of the resistivity as a function of applied current. Magnetic imaging using a superconducting quantum interference device reveals that current switches correspond to reversals of individual magnetic domains. The real space pattern of domain reversals aligns precisely with spin accumulation measured near the high-Berry curvature Hubbard band edges. This suggests that intrinsic spin- or valley-Hall torques drive the observed current-driven magnetic switching in both MoTe2/WSe2 and other moire materials. The switching current density of 10^3 Amps per square centimeter is significantly less than reported in other platforms paving the way for efficient control of magnetic order.
Questions from our internal Board of experts: The original Intrinsic spin Hall effect, based on the anomalous velocity, is a property of a particular band. If there is interband scattering the intrinsic effect is known to be destroyed and intrinsic spin torque presumably is also sensitive to disorder. But you can have skew-scattering-induced extrinsic Hall phenomena. Are your MoTe2/WSe2 systems disordered or clean?
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