Theoretical investigation of the applicability of the Meservey–Tedrow technique to the surface states of topological insulators

Abstract

The spin polarization of topological surface states is of high interest for possible applications in spintronics. At present, the only technique capable to measure the surface state spin texture is spin and angle resolved photoemission spectroscopy (SARPES). However, values reported by SARPES differed strongly. An established technique to measure the spin polarization of ferromagnetic materials is the so-called Meservey–Tedrow technique, which is based on spin dependent tunneling from a superconducting electrode to a ferromagnet. Here, we theoretically investigate how the Meservey–Tedrow technique can be adapted to topological insulators. We demonstrate that with a specific device geometry it is possible to determine the in-plane component of the spin polarization of topological surface states. More complex device geometries can access the full momentum dependence of the spin polarization. We also show that it is possible to extract the spin-flip scattering rate of surface electrons with the same devices.