Surface electronic structures of topological insulators probed by spin-and angle-resolved photoelectron spectroscopy

Abstract

Three-dimensional topological insulators (3D TIs) with a gapless topological surface state in a bulk energy gap induced by a strong spin-orbit coupling have attracted much attention as key materials to revolutionize current electronic devices. A spin helical texture of a topological surface state, where the electron spin is locked to its momentum, is a manifestation of a 3D TI. A number of well-known thermoelectric and phase-change materials have so far been predicted to be 3D TIs. In order to experimentally conform their topological characteristics, spin- and angle- resolved photoemission spectroscopy is one of the most powerful tools and it has actually been playing major roles in finding some real 3D TIs. In this article, after extensive introduction of topological insulators and spin- and angle- resolved photoemission spectroscopy, some of the ternary 3D TIs are shown to possess topological surface states with marked spin polarizations. It has been revealed for GeBi 2 Te 4 that an intermixing effect in the crystal has a minor effect on the surface-state spin polarization, which is ∼70% near the Dirac point in the bulk energy gap region (∼180 meV), which promises to future technological application.