The conversion of charge current to spin current is of considerable current interest from both fundamental and technological perspectives. It can be used to manipulate the magnetization order parameter in spintronic devices such as three terminal magnetic tunnel junction device and the racetrack memory.
Significant conversion of charge current to spin-polarized current is made possible through the spin Hall effect (SHE).
The most exciting development lie in the recognition that many materials possess an intrinsic SHE that is derived from characteristic features in the band structure that are topological in nature. A link has been made between SHE and the Berry field.
Measurement of the spin Hall effect especially for atomically thin systems is not straight forward. While several techniques have been used, the vast majority are limited to metallic ferromagnets that display magnetoresistance and/or have limited sensitivity. To that end the we have recently developed ultra-sensitive phase resolved time domain optical-electrical methods for the measurement of the SHE.
In our recent work [PRB 95, 064401 (2017)] we applied the method to an ultrathin, 4-atom thick, Pt-Co/Ni/Co system whose spin Hall angle was to date characterized only indirectly and that is especially relevant for spin-orbit torque devices.