Spin-to-Charge Conversion in Ag/Bi Bilayer Revisited.

The spin-to-charge conversion of the Ag/Bi interface is studied in a device in which a spin current can be injected from either side selectively. The charge voltages generated by the two counterpropagating spin currents show opposite signs, that is consistent with the inverse spin Hall effect rather than the well-accepted inverse Rashba-Eldestein effect in the Ag/Bi bilayer. Femtosecond laser is further employed to generate the spin-current-induced terahertz signal in a Ag/Bi bilayer, which shows no evidence for the inverse Rashba-Eldestein effect, either. This work provides a clear-cut method to identify the spin-to-charge mechanism in a Rashba electronic state and delivers new understanding for the relevant spin-transport phenomena.