The electronic structure of prototype topological insulators has been studied with ultrafast ARPES, using the ARTOF spectrometer in combination with the femtosecond laser source at the LPS.
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.
Figure.
(a) Normalized difference energy distribution I(E; kx; ky; t) maps measured using L- and R-circularly polarized light in Bi2Te2Se at a delay of +250 fs. (b) Difference isoenergy contour maps at different energies. (c) Similar normalized difference energy distribution maps and (d) isoenergy momentum curves in Bi2Se3
Reference
Probing spin chirality of photoexcited topological insulators with circular dichroism multi-dimensional time-resolved ARPES on Bi2Te2Se and Bi2Se3.
J. Zhang, J. Caillaux, Z. Chen, M. Konczykowski, A. Hruban, A. Wolos, A. Materna, L. Perfetti, E. Papalazarou and M. Marsi
doi: 10.1016/j.elspec.2021.147125