Surface states mediated spin-to-charge conversion in Bi1-xSbx/Co and Bi2SnTe4/Co topological insulators probed by THz emission spectroscopy. (Conference Presentation)

Abstract

We report the terahertz (THz) emission from Bi1-xSbx/Co and Bi2SnTe4/Co bilayers including nanometer-thin ferromagnetic layer as spin-injectors and Bi1-xSbx and Bi2SnTe4 topological insulators (TI) from the Bi family grown by molecular beam epitaxy. Using THz emission spectroscopy, an efficient dynamical spin-to-charge conversion in the sub-picosecond timescale is demonstrated in these heterostructures with an output THz amplitude sizeable compared to reference metallic spintronic THz emitters. We investigate TI thickness dependence and azimuthal crystalline orientation dependence on the THz emission which are both in line with interfacially-mediated interconversion. We show that a strong reminiscent THz signal at the limit of small TI thickness is explained by a spin-charge interconversion occurring at the level of the first planes of their interface in contact with Co. This strongly suggests a spin-charge interconversion via inverse Rashba-Edelstein effect (IREE) onto spin-locked TI’s interface states.