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Title: Surface collective modes in the topological insulators Bi2Se3 and Bi0.5Sb1.5Te3-xSex

In this study, we used low-energy, momentum-resolved inelastic electron scattering to study surface collective modes of the three-dimensional topological insulators Bi2Se3 and Bi0.5Sb1.5Te3-xSex. Our goal was to identify the “spin plasmon” predicted by Raghu and co-workers [Phys. Rev. Lett. 104, 116401 (2010)]. Instead, we found that the primary collective mode is a surface plasmon arising from the bulk, free carriers in these materials. This excitation dominates the spectral weight in the bosonic function of the surface χ''(q,ω) at THz energy scales, and is the most likely origin of a quasiparticle dispersion kink observed in previous photoemission experiments. Our study suggests that the spin plasmon may mix with this other surface mode, calling for a more nuanced understanding of optical experiments in which the spin plasmon is reported to play a role.
Authors:
 [1] ;  [2] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [3] ;  [2] ;  [2] ;  [2] ;  [2] ;  [1] ;  [1] ;  [1] ;  [1]
  1. Univ. of Illinois, Urbana, IL (United States)
  2. Brookhaven National Lab. (BNL), Upton, NY (United States)
  3. Korea Advanced Institute of Science and Technology, Daejeon (Korea)
Publication Date:
OSTI Identifier:
1240702
Report Number(s):
BNL--111864-2016-JA
Journal ID: ISSN 0031-9007; PRLTAO; R&D Project: PO010; PO016; KC0201060; KC0202020
Grant/Contract Number:
SC00112704
Type:
Accepted Manuscript
Journal Name:
Physical Review Letters
Additional Journal Information:
Journal Volume: 115; Journal Issue: 25; Journal ID: ISSN 0031-9007
Publisher:
American Physical Society (APS)
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY