Selective probing of photoinduced charge and spin dynamics in the bulk and surface of a topological insulator

D. Hsieh, F. Mahmood, J. W. McIver, D. R. Gardner, Y. S. Lee, N. Gedik

Research output: Contribution to journalArticle

Abstract

Topological insulators possess completely different spin-orbit coupled bulk and surface electronic spectra that are each predicted to exhibit exotic responses to light. Here we report time-resolved fundamental and second harmonic optical pump-probe measurements on the topological insulator Bi 2Se3 to independently measure its photoinduced charge and spin dynamics with bulk and surface selectivity. Our results show that a transient net spin density can be optically induced in both the bulk and surface, which may drive spin transport in topological insulators. By utilizing a novel rotational anisotropy analysis we are able to separately resolve the spin depolarization, intraband cooling, and interband recombination processes following photoexcitation, which reveal that spin and charge degrees of freedom relax on very different time scales owing to strong spin-orbit coupling.

Original languageEnglish (US)
Article number077401
JournalPhysical review letters
Volume107
Issue number7
DOIs
StatePublished - Aug 10 2011
Externally publishedYes

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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