Spin-conserving and reversing photoemission from the surface states of Bi2Se3 and Au(111)

Abstract

We present a theory based on first-principles calculations explaining (i) why the tunability of spin polarizations of photoelectrons from Bi2Se3 (111) depends on the band index and Bloch wave vector of the surface state and (ii) why such tunability is absent in the case of isosymmetric Au (111). The results provide not only an explanation for the recent, puzzling experimental observations but also a guide toward making highly-tunable spin-polarized electron sources from topological insulators.