The demonstration of current-induced spin-orbit torques (SOT) in thin-film systems has provided exciting new ways to harness spin-charge conversion and generate non-equilibrium spin populations at the device level. In this talk, I will present our recent research on the SOT phenomena in thin-film heterostructures grown via molecular beam epitaxy.

In the first part, I will discuss the charge-to-spin conversion in two topological semimetals, Cd3As2 (Dirac semimetal) and TaAs (Weyl semimetal). When these semimetals are in the pristine state, by using the technique of spin-torque ferromagnetic resonance, we experimentally show their spin-Hall conductivities quantitatively agree with results computed from first principles. We also observe that the SOT in these topological semimetals can be enhanced in the presence of an oxidized interface.

In the second part, I will report the synthesis and characterizations of a full van der Waals epitaxial heterostructure consisting of a Dirac semimetal, ZrTe2, and a two-dimensional ferromagnet, CrTe2. We observe robust ferromagnetism in CrTe2 thin films down to one-unit-cell thickness. Furthermore, anomalous Hall measurements suggest the existence of chiral magnetic structures in in thicker CrTe2 films. Finally, we demonstrate SOT-assisted magnetization switching in the CrTe2 via the current-induced spin-torques from ZrTe2.