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Kogar A, Vig S, Thaler A, Wong MH, Xiao Y, Reig-I-Plessis D, Cho GY, Valla T, Pan Z, Schneeloch J, Zhong R, Gu GD, Hughes TL, MacDougall GJ, Chiang TC, Abbamonte P. Surface Collective Modes in the Topological Insulators Bi_{2}Se_{3} and Bi_{0.5}Sb_{1.5}Te_{3-x}Se_{x}. Phys Rev Lett 2015; 115:257402. [PMID: 26722943 DOI: 10.1103/physrevlett.115.257402] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Indexed: 06/05/2023]
Abstract
We used low-energy, momentum-resolved inelastic electron scattering to study surface collective modes of the three-dimensional topological insulators Bi_{2}Se_{3} and Bi_{0.5}Sb_{1.5}Te_{3-x}Se_{x}. 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.
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Affiliation(s)
- A Kogar
- Department of Physics and Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, USA
| | - S Vig
- Department of Physics and Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, USA
| | - A Thaler
- Department of Physics and Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, USA
| | - M H Wong
- Department of Physics and Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, USA
| | - Y Xiao
- Department of Physics and Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, USA
| | - D Reig-I-Plessis
- Department of Physics and Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, USA
| | - G Y Cho
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea
| | - T Valla
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Z Pan
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - J Schneeloch
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - R Zhong
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - G D Gu
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - T L Hughes
- Department of Physics and Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, USA
| | - G J MacDougall
- Department of Physics and Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, USA
| | - T-C Chiang
- Department of Physics and Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, USA
| | - P Abbamonte
- Department of Physics and Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, USA
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