Elmers, H.J.; Wallauer, R.; Liebmann, M.; Kellner, J.; Morgenstern, M.; Wang, R.N.; Boschker, J.E.; Calarco, R.; Sánchez-Barriga, J.; Rader, O.; Kutnyakhov, D.; Chernov, S.V.; Medjanik, K.; Tusche, C.; Ellguth, M.; Volfova, H.; Borek, St.; Braun, J.; Minar, J.; Ebert, H.; Schoenhense, G.: Spin mapping of surface and bulk Rashba states in ferroelectric alpha-GeTe(111) films. Physical Review B 94 (2016), p. 201403/1-5
Open Accesn Version

The breaking of bulk inversion symmetry in ferroelectric semiconductors causes a Rashba-type spin splitting of electronic bulk bands. This is shown by a comprehensive mapping of the spin polarization of the electronic bands in ferroelectric α-GeTe(111) films using a time-of-flight momentum microscope equipped with an imaging spin filter that enables a simultaneous measurement of more than 10 000 data points. The experiment reveals an opposite spin helicity of the inner and outer Rashba bands with a different spin polarization in agreement with theoretical predictions, confirming a complex spin texture of bulk Rashba states. The outer band has about twice larger spin polarization than the inner one, giving evidence of a spin-orbit effect being related to the orbital composition of the band states. The switchable inner electric field of GeTe implies new functionalities for spintronic devices.