Photoemission Circular Dichroism and Spin Polarization of the Topological Surface States in Ultrathin ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$ Films

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Photoemission Circular Dichroism and Spin Polarization of the Topological Surface States in Ultrathin ${Bi}_{2} {Te}_{3}$ Films

C.-Z. Xu, Y. Liu, R. Yukawa, L.-X. Zhang, I. Matsuda, T. Miller, and T.-C. Chiang

Phys. Rev. Lett. 115, 016801 – Published 30 June 2015

Abstract

Circular dichroism (CD) observed by photoemission, being sensitive to the orbital and spin angular momenta of the electronic states, is a powerful probe of the nontrivial surface states of topological insulators, but the experimental results thus far have eluded a comprehensive description. We report a study of ${Bi}_{2} {Te}_{3}$ films with thicknesses ranging from one quintuple layer (two-dimensional limit) to 12 layers (bulk limit) over a wide range of incident photon energy. The data show complex variations in magnitude and sign reversals, which are nevertheless well described by a theoretical calculation including all three photoemission mechanisms: dipole transition, surface photoemission, and spin-orbit coupling. The results establish the nontrivial connection between the spin-orbit texture and CD.

Received 13 March 2015

DOI:https://doi.org/10.1103/PhysRevLett.115.016801

Authors & Affiliations

C.-Z. Xu¹, Y. Liu^1,2, R. Yukawa³, L.-X. Zhang¹, I. Matsuda³, T. Miller¹, and T.-C. Chiang¹

¹Department of Physics and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
²X-ray science division, Argonne National Lab, 9700 South Cass Avenue, Lemont, Illinois 60439, USA
³Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan