UC Berkeley

Understanding the fine interplay between spin and orbital degrees of freedom in the surface states of topological insulators is the key to the development of next-generation spintronics devices. So far, the majority of studies have focused on the helical spin texture of the topologically protected surface state (TSS) and little attention has been devoted to the spin texture of the other surface states: the bulk-originated quantum well states (QWSs). This paper presents such study in a prototypical topological insulator, Bi2Se3. By using spin- and angle-resolved photoemission spectroscopy, we reveal a full momentum-dependent spin texture of the QWSs and their response to light polarization. We find that these states share a similar spin-orbital texture with the TSS. This paper shows an intimate correlation between the surface and bulk states, which was overseen before, and provides relevant information to understand how the surface states evolve with the bulk states.