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Title: Superconducting pairing of topological surface states in bismuth selenide films on niobium

Abstract

A topological insulator film coupled to a simple isotropic s-wave superconductor substrate can foster helical pairing of the Dirac fermions associated with the topological surface states. Experimental realization of such a system is exceedingly difficult, however using a novel “flip-chip” technique, we have prepared single-crystalline Bi 2Se 3 films with predetermined thicknesses in terms of quintuple layers (QLs) on top of Nb substrates fresh from in situ cleavage. Our angle-resolved photoemission spectroscopy (ARPES) measurements of the film surface disclose superconducting gaps and coherence peaks of similar magnitude for both the topological surface states and bulk states. The ARPES spectral map as a function of temperature and film thickness up to 10 QLs reveals key characteristics relevant to the mechanism of coupling between the topological surface states and the superconducting Nb substrate; the effective coupling length is found to be much larger than the decay length of the topological surface states.

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [1];  [1]; ORCiD logo [2];  [2]; ORCiD logo [2]; ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [1]
  1. Univ. of Illinois, Urbana, IL (United States)
  2. Univ. of Tokyo (Japan)
Publication Date:
Research Org.:
Univ. of Illinois at Urbana-Champaign, IL (United States); Iowa State Univ., Ames, IA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1499947
Grant/Contract Number:  
[FG02-07ER46383; AC02-07CH11358]
Resource Type:
Accepted Manuscript
Journal Name:
Science Advances
Additional Journal Information:
[ Journal Volume: 4; Journal Issue: 4]; Journal ID: ISSN 2375-2548
Publisher:
AAAS
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY

Citation Formats

Flötotto, David, Ota, Yuichi, Bai, Yang, Zhang, Can, Okazaki, Kozo, Tsuzuki, Akihiro, Hashimoto, Takahiro, Eckstein, James N., Shin, Shik, and Chiang, Tai-Chang. Superconducting pairing of topological surface states in bismuth selenide films on niobium. United States: N. p., 2018. Web. doi:10.1126/sciadv.aar7214.
Flötotto, David, Ota, Yuichi, Bai, Yang, Zhang, Can, Okazaki, Kozo, Tsuzuki, Akihiro, Hashimoto, Takahiro, Eckstein, James N., Shin, Shik, & Chiang, Tai-Chang. Superconducting pairing of topological surface states in bismuth selenide films on niobium. United States. doi:10.1126/sciadv.aar7214.
Flötotto, David, Ota, Yuichi, Bai, Yang, Zhang, Can, Okazaki, Kozo, Tsuzuki, Akihiro, Hashimoto, Takahiro, Eckstein, James N., Shin, Shik, and Chiang, Tai-Chang. Fri . "Superconducting pairing of topological surface states in bismuth selenide films on niobium". United States. doi:10.1126/sciadv.aar7214. https://www.osti.gov/servlets/purl/1499947.
@article{osti_1499947,
title = {Superconducting pairing of topological surface states in bismuth selenide films on niobium},
author = {Flötotto, David and Ota, Yuichi and Bai, Yang and Zhang, Can and Okazaki, Kozo and Tsuzuki, Akihiro and Hashimoto, Takahiro and Eckstein, James N. and Shin, Shik and Chiang, Tai-Chang},
abstractNote = {A topological insulator film coupled to a simple isotropic s-wave superconductor substrate can foster helical pairing of the Dirac fermions associated with the topological surface states. Experimental realization of such a system is exceedingly difficult, however using a novel “flip-chip” technique, we have prepared single-crystalline Bi2Se3 films with predetermined thicknesses in terms of quintuple layers (QLs) on top of Nb substrates fresh from in situ cleavage. Our angle-resolved photoemission spectroscopy (ARPES) measurements of the film surface disclose superconducting gaps and coherence peaks of similar magnitude for both the topological surface states and bulk states. The ARPES spectral map as a function of temperature and film thickness up to 10 QLs reveals key characteristics relevant to the mechanism of coupling between the topological surface states and the superconducting Nb substrate; the effective coupling length is found to be much larger than the decay length of the topological surface states.},
doi = {10.1126/sciadv.aar7214},
journal = {Science Advances},
number = [4],
volume = [4],
place = {United States},
year = {2018},
month = {4}
}

Journal Article:
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Cited by: 2 works
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Figures / Tables:

Fig. 1. Fig. 1.: Cleavage-based sample preparation and characterization. (A) Photo and schematic diagram of assembled Bi2Se3(0001)/Nb sample structure before cleavage. (B) Same sample structure after cleavage exposing a “fresh” surface of the Bi2Se3 film with a predetermined thickness of four QLs. (C) ARPES maps for samples with 4, 7, and 10more » QLs of Bi2Se3 films. The spectra were recorded at photon energies of 18, 35, and 35 eV, respectively. (D) An x-ray photoelectron spectroscopy spectrum taken from a cleaved-off Al2O3 substrate reveals that only a trace amount of Bi is left on the substrate after cleavage, thus confirming that the cleavage occurs at the Bi2Se3/Al2O3 interface. (E) Atomic force microscopy (AFM)image of the Bi2Se3 film surface after cleavage. The step structure corresponds well to that of the Al2O3 substrate. a.u., arbitrary units.« less

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    Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.