Toward efficient spin/charge conversion using topological insulator surface (Conference Presentation)
Résumé
Band gap opening and TI properties can be induced at room temperature in α-Sn (001) thin films by strain and quantum finite-size effects. Indeed, angle-resolved photoemission spectroscopy (ARPES) measurements by Ohtsubo et al. performed on thin α-Sn (001) films grown in-situ by molecular beam epitaxy revealed a Dirac cone (DC) linear dispersion with helical spin polarization around the Γ point of the surface Brillouin zone. We recently reported that a very efficient spin-to-charge conversion (SCC) can be achieved at room temperature by spin pumping into this α-Sn thin films, in clear relation with the inverse Edelstein effect (IEE) induced by the counterclockwise helical spin configuration of the DC identified by ARPES . We will present our work focused on the research of efficient interface for charge current to spin current. We will be discuss in details our study by ARPES of the thickness dependence, as well as the impact of a metallic or insulating capping layer on the α-Sn surface states. For all the thicknesses (20 to 50 atomic layers) a linear energy dispersion of the surface states has been observed, allowing the Fermi velocity, the Fermi level and the density of states to be estimated. Following ARPES experiments we performed magneto-transport experiments using the same samples. It is then possible by tracking the Shubnikov-de Haas oscillations to evidence the signature of the surface states, supporting that transport measurements can indeed reveal surface states.