QDev Seminar: David MacNeill
Ralph Group, nanoscale physics, Cornell University
Spin-orbit torques from broken crystal symmetries in transition-metal dichalcogenide/ferromagnet bilayers
Mechanisms for manipulating nanoscale magnets that are driven by spin-orbit coupling, such as the spin Hall and Rashba-Edelstein effects, provide a novel solution for electrically switching magnetic memory bits. However, these mechanisms are only efficient for a limited subset of magnetic configurations -- a limitation imposed by the structural symmetries of conventional devices. One approach to overcome this limitation is to use a low-symmetry crystalline spin source material. Layered transition metal dichalcogenides are a natural choice in this investigation, due to their high spin-orbit coupling, varied crystal structures, and straightforward preparation of single-crystal films with atomically flat surfaces. In this talk, I will present recent measurements of current-induced spin-orbit torques in a ferromagnet deposited on the layered material WTe2. Our measurements demonstrate a previously unobserved form of spin-orbit torque, consistent with the low symmetry of the WTe2 surface. I will also briefly discuss spin-orbit torque measurements for other layered transition metal dichalcogenides, and future directions for optimizing spin-orbit torques from reduced structural symmetries.