Oscillatory surface dichroism of the insulating topological insulator Bi${}_{2}$Te${}_{2}$Se

Oscillatory surface dichroism of the insulating topological insulator Bi $_{2}$ Te $_{2}$ Se

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

Phys. Rev. B 88, 165129 – Published 21 October 2013

Abstract

Using circular dichroism-angle resolved photoemission spectroscopy, we report a study of the effect of angular momentum transfer between polarized photons and topological surface states on the surface of the insulating topological insulator Bi $_{2}$ Te $_{2}$ Se. 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 opto-spintronics device applications.

Received 30 July 2013

DOI:https://doi.org/10.1103/PhysRevB.88.165129

Authors & Affiliations

M. Neupane¹, S. Basak², N. Alidoust¹, S.-Y. Xu¹, Chang Liu¹, I. Belopolski¹, G. Bian¹, J. Xiong¹, H. Ji³, S. Jia³, S.-K. Mo⁴, M. Bissen⁵, M. Severson⁵, H. Lin², N. P. Ong¹, T. Durakiewicz⁶, R. J. Cava³, A. Bansil², and M. Z. Hasan^1,7,*

¹Joseph Henry Laboratory and Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
²Department of Physics, Northeastern University, Boston, Massachusetts 02115, USA
³Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA
⁴Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94305, USA
⁵Synchrotron Radiation Center, Stoughton, Wisconsin 53589-3097, USA
⁶Condensed Matter and Magnet Science Group, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
⁷Princeton Center for Complex Materials, Princeton University, Princeton, New Jersey 08544, USA

^*Author to whom correspondence and requests for materials should be addressed: mzhasan@princeton.edu

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Vol. 88, Iss. 16 — 15 October 2013

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Images

Figure 1
(a) Crystal structure of BTS221. Red, green, and blue circles represent the Se, Bi, and Te atoms, respectively. (b) Normalized in-plane resistivities ( $R / R_{300}$ ) plotted as a function of temperature ( $T$ ) for BTS221. The resistivity profiles of Bi $_{2}$ Se $_{3}$ and Bi $_{2}$ Te $_{3}$ are added for comparison. Insets show the Fermi surface plots for BTS221 (upper panel) and Bi $_{2}$ Te $_{3}$ (lower panel). Arrows around the FS represent the in-plane spin texture. (c) Shubnikov-de Haas oscillation measurements on the topological surface of BTS221 (see Ref. 30 for details).Reuse & Permissions
Figure 2
(a) High-resolution ARPES measurements of Bi $_{2}$ Te $_{2}$ Se for right circularly polarized (RCP) light, left circularly polarized (LCP) light and the photoelectron circular dichroism ( $I_{R C P} - I_{L C P}$ ) measured with photon energy $ω_{1} = 18$ eV. (b) Analogous measurements as in (a) for photon energy $ω_{2} = 23$ eV. These spectra are measured along the $\bar{Γ} - \bar{M}$ high symmetry momentum-space cut. (c) The measured CD values for binding energies of 50 meV and 100 meV as marked on the $I_{C D}$ plot of (a) by black dashed lines and denoted by numbers 1 and 2. (d) Similar measurements as (c) for (b). (e) and (f) The momentum distribution curves of CD spectra for 18 eV and 23 eV photons, respectively.Reuse & Permissions
Figure 3
ARPES data demonstrating oscillations in the CD signal. Raw data of high-resolution ARPES measurements of BTS221 for 19 eV, 20 eV, 22 eV, 23 eV, 24 eV, 28 eV, 29 eV, and 31 eV with right circularly polarized (RCP) light (top row), with left circularly polarized (LCP) light (middle row), and the circular dichroism (RCP-LCP) (bottom row). These plots provide a direct visualization of the oscillatory behavior of the surface CD signal. The measured photon energies are noted on the spectra.Reuse & Permissions
Figure 4
(a) The measured CD values are plotted as a function of photon energy. The photoelectron CD value is estimated as $I_{C D} = (I^{+} - I^{-}$ )/( $I^{+} + I^{-}$ ) for data taken with momentum $k \sim - 0.05$ $Å^{- 1}$ and binding energy $\sim$ 100 meV. Arrows represent the photon energies of representative CD-ARPES spectra presented in (b). Inset shows the geometry of the ARPES measurement (see text for details). (b) ARPES plots of the circular dichroic photoemission with various photon energies. The corresponding photon energies are noted on the plots. The spectra taken with 20–23 eV exhibit negative CD values (top row) while it is taken with 24–31 eV exhibit positive CD values (bottom row).Reuse & Permissions
Figure 5
Oscillatory dichroism in other TI systems. (a) ARPES measurements of Bi $_{1.4}$ Sb $_{0.6}$ Te $_{1.5}$ S $_{1.5}$ for right circularly polarized (RCP) light, left circularly polarized (LCP) light and the circular dichroism (RCP-LCP). The top row spectra are measured with photon energy 19 eV while the bottom row spectra are measured with photon energy 22 eV. (b) ARPES measurements of Bi $_{2}$ Te $_{3}$ for right circularly polarized (RCP) light, left circularly polarized (LCP) light and the circular dichroism (RCP-LCP). The top row spectra are measured with photon energy 29 eV while the bottom row spectra are measured with photon energy 31 eV. These results suggest that the oscillatory behavior of the CD response is a more general property of topological insulators.Reuse & Permissions
Figure 6
Model calculations are carried out for photon energies of (a) 21 eV and 22 eV, and (b) 24 eV and 25 eV. The change in the sign of CD can be observed by comparing spectra shown in (a) and (b). (c) The theoretically calculated $I_{C D}$ at constant $k_{x}$ and $E$ as a function of photon energy. The black arrow indicates the photon energy value where flipping of CD sign is expected in our theoretical model for BTS221.Reuse & Permissions

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