Probing spin chirality of photoexcited topological insulators with circular dichroism: multi-dimensional time-resolved ARPES on Bi2Te2Se and Bi2Se3

Using time-resolved multi-dimensional angle-resolved photoelectron spectroscopy (ARPES) we explore the angular momentum transfer of low energy polarized photons to two prototype topological insulators, Bi2Te2Se and Bi2Se3. Our comparative study is based on the analysis of circular dichroism in the photoemission yield of photoexcited Dirac states, and reveals that the spin vector of in-gap Dirac electrons in Bi2Te2Se presents a more pronounced out-of-plane component compared to that of Bi2Se3. We show that the multi-dimensional ARPES approach can be effectively used to observe the spin texture of photoexcited topological insulators, and to unambiguously disentangle experimental geometry and matrix element effects.

Automated summary

Using time-resolved multi-dimensional angle-resolved photoelectron spectroscopy, this study investigated the angular momentum transfer of low energy polarized photons to two prototype topological insulators. It was found that the spin vector of in-gap Dirac electrons in Bi2Te2Se has a more pronounced out-of-plane component compared to Bi2Se3. The multi-dimensional ARPES approach was demonstrated to effectively observe the spin texture of photoexcited topological insulators and differentiate experimental geometry and matrix element effects.