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

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"...

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Bibliographic Details
Published in:Science advances 2018-04, Vol.4 (4), p.eaar7214-eaar7214
Main Authors: Flötotto, David, Ota, Yuichi, Bai, Yang, Zhang, Can, Okazaki, Kozo, Tsuzuki, Akihiro, Hashimoto, Takahiro, Eckstein, James N, Shin, Shik, Chiang, Tai-Chang
Format: Article
Language:English
Subjects:
Condensed Matter Physics
CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
MATERIALS SCIENCE
SciAdv r-articles
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Summary: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 Se 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.
ISSN:2375-2548
2375-2548
DOI:10.1126/sciadv.aar7214