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Title: Proximity-effect-induced Superconducting Gap in Topological Surface States – A Point Contact Spectroscopy Study of NbSe 2/Bi 2Se 3 Superconductor-Topological Insulator Heterostructures

Proximity-effect-induced superconductivity was studied in epitaxial topological insulator Bi 2Se 3 thin films grown on superconducting NbSe 2 single crystals. A point contact spectroscopy (PCS) method was used at low temperatures down to 40 mK. An induced superconducting gap in Bi 2Se 3 was observed in the spectra, which decreased with increasing Bi 2Se 3 layer thickness, consistent with the proximity effect in the bulk states of Bi 2Se 3 induced by NbSe 2. At very low temperatures, an extra point contact feature which may correspond to a second energy gap appeared in the spectrum. For a 16 quintuple layer Bi 2Se 3 on NbSe 2 sample, the bulk state gap value near the top surface is ~159 μeV, while the second gap value is ~120 μeV at 40 mK. The second gap value decreased with increasing Bi 2Se 3 layer thickness, but the ratio between the second gap and the bulk state gap remained about the same for different Bi 2Se 3 thicknesses. It is plausible that this is due to superconductivity in Bi 2Se 3 topological surface states induced through the bulk states. In conclusion, the two induced gaps in the PCS measurement are consistent with the three-dimensionalmore » bulk state and the two-dimensional surface state superconducting gaps observed in the angle-resolved photoemission spectroscopy (ARPES) measurement.« less
Authors:
ORCiD logo [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [2] ;  [2] ; ORCiD logo [1] ; ORCiD logo [1]
  1. The Pennsylvania State Univ., University Park, PA (United States)
  2. National Taiwan Univ., Taipei (Taiwan)
Publication Date:
Grant/Contract Number:
FG02-08ER46531; SC0005042
Type:
Accepted Manuscript
Journal Name:
Scientific Reports
Additional Journal Information:
Journal Volume: 7; Journal Issue: 1; Journal ID: ISSN 2045-2322
Publisher:
Nature Publishing Group
Research Org:
Pennsylvania State Univ., University Park, PA (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
OSTI Identifier:
1465870