Oscillatory surface dichroism of an insulating topological insulator Bi2Te2Se
M. Neupane, S. Basak, N. Alidoust, S.-Y. Xu, Chang Liu, I. Belopolski,, G. Bian, J. Xiong, H. Ji, S. Jia, S.-K. Mo, M. Bissen, M. Severson, H. Lin,, N. P. Ong, T. Durakiewicz, R. J. Cava, A. Bansil, and M. Z. Hasan
TL;DR
This study uses CD-ARPES to explore how polarized light interacts with surface states of a bulk-insulating topological insulator, revealing strong modulation and sign-flip in dichroism due to photon-spin coupling.
Contribution
It demonstrates the intrinsic dichroic behavior of topological surface states and highlights the influence of photon frequency on dichroism in Bi2Te2Se.
Findings
Dichroism is strongly modulated by photon frequency.
Sign-flip in dichroism observed with changing photon energy.
Strong coupling between photons and spin-orbit surface states.
Abstract
Using circular dichroism-angle resolved photoemission spectroscopy (CD-ARPES), we report a study of the effect of angular momentum transfer between polarized photons and topological surface states on the surface of highly bulk insulating topological insulator Bi2Te2Se. The photoelectron dichroism is found to be strongly modulated by the frequency of the helical photons including a dramatic sign-flip. Our results suggest that the observed dichroism and its sign-flip are consequences of strong coupling between the photon field and the spin-orbit nature of the Dirac modes on the surface. Our studies reveal the intrinsic dichroic behavior of topological surface states and point toward the potential utility of bulk insulating topological insulators in device applications.
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