title: Observation of a warped helical spin texture in Bi2Se3 from circular dichroism angle-resolved photoemission spectroscopy.
abstract: A differential coupling of topological surface states to left- versus right-circularly polarized light is the basis of many optospintronics applications of topological insulators. Here we report direct evidence of circular dichroism from the surface states of Bi(2)Se(3) using laser-based time-of-flight angle-resolved photoemission spectroscopy. By employing a novel sample rotational analysis, we resolve unusual modulations in the circular dichroism photoemission pattern as a function of both energy and momentum, which perfectly mimic the predicted but hitherto unobserved three-dimensional warped spin texture of the surface states. By developing a microscopic theory of photoemission from topological surface states, we show that this correlation is a natural consequence of spin-orbit coupling. These results suggest that our technique may be a powerful probe of the spin texture of spin-orbit coupled materials in general.
authors.affiliation: Department of Physics, Massachusetts Institute of Technology, Cambridge, 02139, USA.
authors.forename: Y H
authors.initials: YH
authors.lastname: Wang
authors.forename: D
authors.initials: D
authors.lastname: Hsieh
authors.forename: D
authors.initials: D
authors.lastname: Pilon
authors.forename: L
authors.initials: L
authors.lastname: Fu
authors.forename: D R
authors.initials: DR
authors.lastname: Gardner
authors.forename: Y S
authors.initials: YS
authors.lastname: Lee
authors.forename: N
authors.initials: N
authors.lastname: Gedik