Coexistence of large conventional and planar spin Hall effect with long spin diffusion length in a low-symmetry semimetal at room temperature

A large spin Hall angle and long spin diffusion length are found in the low-symmetry, few-layer semimetal MoTe2 at room temperature, thus identifying this material as an excellent candidate for simultaneous spin generation, transport and detection. The spin Hall effect (SHE) is usually observed as a bulk effect in high-symmetry crystals with substantial spin-orbit coupling (SOC), where the symmetric spin-orbit field imposes a widely encountered trade-off between spin Hall angle (theta(SH)) and spin diffusion length (L-sf), and spin polarization, spin current and charge current are constrained to be mutually orthogonal. Here, we report a large theta(SH) of 0.32 accompanied by a long L-sf of 2.2 mu m at room temperature in a low-symmetry few-layered semimetal MoTe2, thus identifying it as an excellent candidate for simultaneous spin generation, transport and detection. In addition, we report that longitudinal spin current with out-of-plane polarization can be generated by both transverse and vertical charge current, due to the conventional and a newly observed planar SHE, respectively. Our study suggests that manipulation of crystalline symmetries and strong SOC opens access to new charge-spin interconversion configurations and spin-orbit torques for spintronic applications.