Ultrafast optical excitation of a persistent surface-state population in the topological insulator Bi2Se3

Phys Rev Lett. 2012 Mar 16;108(11):117403. doi: 10.1103/PhysRevLett.108.117403. Epub 2012 Mar 14.

Abstract

Using femtosecond time- and angle-resolved photoemission spectroscopy, we investigated the nonequilibrium dynamics of the topological insulator Bi2Se3. We studied p-type Bi2Se3, in which the metallic Dirac surface state and bulk conduction bands are unoccupied. Optical excitation leads to a metastable population at the bulk conduction band edge, which feeds a nonequilibrium population of the surface state persisting for >10 ps. This unusually long-lived population of a metallic Dirac surface state with spin texture may present a channel in which to drive transient spin-polarized currents.