The effect of substrate and surface plasmons on symmetry breaking at the substrate interface of the topological insulator Bi2Te3

Maciej Wiesner; Richard H Roberts; Jung-Fu Lin; Deji Akinwande; Thorsten Hesjedal; Liam B Duffy; Shumin Wang; Yuxin Song; Jacek Jenczyk; Stefan Jurga; Boguslaw Mroz

doi:10.1038/s41598-019-42598-9

The effect of substrate and surface plasmons on symmetry breaking at the substrate interface of the topological insulator Bi₂Te₃

Sci Rep. 2019 Apr 16;9(1):6147. doi: 10.1038/s41598-019-42598-9.

Authors

Maciej Wiesner^{1

2}, Richard H Roberts^{3

4}, Jung-Fu Lin^{4

5}, Deji Akinwande^{3

4}, Thorsten Hesjedal⁶, Liam B Duffy⁶, Shumin Wang^{7

8}, Yuxin Song⁷, Jacek Jenczyk⁹, Stefan Jurga⁹, Boguslaw Mroz¹⁰

Affiliations

¹ Faculty of Physics, Adam Mickiewicz University, Umultowska 85, PL61614, Poznan, Poland. mwiesner@amu.edu.pl.
² Microelectronics Research Center, The University of Texas at Austin, TX78757, Austin, USA. mwiesner@amu.edu.pl.
³ Microelectronics Research Center, The University of Texas at Austin, TX78757, Austin, USA.
⁴ Texas Materials Institute, The University of Texas at Austin, 78757, Austin, TX, USA.
⁵ Department of Geological Sciences, Jackson School of Geosciences, The University of Texasat Austin, 78712, Austin, TX, USA.
⁶ Clarendon Laboratory, Department of Physics, Parks Road, University of Oxford, Oxford, OX1 3PU, United Kingdom.
⁷ Key Laboratory of Terahertz Solid State Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai, 200050, People's Republic of China.
⁸ Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-412 96, Göteborg, Sweden.
⁹ NanoBioMedical Centre, Adam Mickiewicz University, Umultowska 85, PL 61614, Poznan, Poland.
¹⁰ Faculty of Physics, Adam Mickiewicz University, Umultowska 85, PL61614, Poznan, Poland.

Abstract

A pressing challenge in engineering devices with topological insulators (TIs) is that electron transport is dominated by the bulk conductance, and so dissipationless surface states account for only a small fraction of the conductance. Enhancing the surface-to-volume ratio is a common method to enhance the relative contribution of such states. In thin films with reduced thickness, the confinement results in symmetry-breaking and is critical for the experimental observation of topologically protected surface states. We employ micro-Raman and tip-enhanced Raman spectroscopy to examine three different mechanisms of symmetry breaking in Bi₂Te₃ TI thin films: surface plasmon generation, charge transfer, and application of a periodic strain potential. These mechanisms are facilitated by semiconducting and insulating substrates that modify the electronic and mechanical conditions at the sample surface and alter the long-range interactions between Bi₂Te₃ and the substrate. We confirm the symmetry breaking in Bi₂Te₃ via the emergence of the Raman-forbidden [Formula: see text] mode. Our results suggest that topological surface states can exist at the Bi₂Te₃/substrate interface, which is in a good agreement with previous theoretical results predicting the tunability of the vertical location of helical surface states in TI/substrate heterostructures.