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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

Dai, Wenqing, Richardella, Anthony, Du, Renzhong, Zhao, Weiwei, Liu, Xin, Liu, C. X., Huang, Song -Hsun, Sankar, Raman, Chou, Fangcheng, Samarth, Nitin, and Li, Qi. Proximity-effect-induced Superconducting Gap in Topological Surface States – A Point Contact Spectroscopy Study of NbSe2/Bi2Se3 Superconductor-Topological Insulator Heterostructures. United States: N. p., Web. doi:10.1038/s41598-017-07990-3.
Dai, Wenqing, Richardella, Anthony, Du, Renzhong, Zhao, Weiwei, Liu, Xin, Liu, C. X., Huang, Song -Hsun, Sankar, Raman, Chou, Fangcheng, Samarth, Nitin, & Li, Qi. Proximity-effect-induced Superconducting Gap in Topological Surface States – A Point Contact Spectroscopy Study of NbSe2/Bi2Se3 Superconductor-Topological Insulator Heterostructures. United States. doi:10.1038/s41598-017-07990-3.
Dai, Wenqing, Richardella, Anthony, Du, Renzhong, Zhao, Weiwei, Liu, Xin, Liu, C. X., Huang, Song -Hsun, Sankar, Raman, Chou, Fangcheng, Samarth, Nitin, and Li, Qi. 2017. "Proximity-effect-induced Superconducting Gap in Topological Surface States – A Point Contact Spectroscopy Study of NbSe2/Bi2Se3 Superconductor-Topological Insulator Heterostructures". United States. doi:10.1038/s41598-017-07990-3. https://www.osti.gov/servlets/purl/1465870.
@article{osti_1465870,
title = {Proximity-effect-induced Superconducting Gap in Topological Surface States – A Point Contact Spectroscopy Study of NbSe2/Bi2Se3 Superconductor-Topological Insulator Heterostructures},
author = {Dai, Wenqing and Richardella, Anthony and Du, Renzhong and Zhao, Weiwei and Liu, Xin and Liu, C. X. and Huang, Song -Hsun and Sankar, Raman and Chou, Fangcheng and Samarth, Nitin and Li, Qi},
abstractNote = {Proximity-effect-induced superconductivity was studied in epitaxial topological insulator Bi2Se3 thin films grown on superconducting NbSe2 single crystals. A point contact spectroscopy (PCS) method was used at low temperatures down to 40 mK. An induced superconducting gap in Bi2Se3 was observed in the spectra, which decreased with increasing Bi2Se3 layer thickness, consistent with the proximity effect in the bulk states of Bi2Se3 induced by NbSe2. 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 Bi2Se3 on NbSe2 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 Bi2Se3 layer thickness, but the ratio between the second gap and the bulk state gap remained about the same for different Bi2Se3 thicknesses. It is plausible that this is due to superconductivity in Bi2Se3 topological surface states induced through the bulk states. In conclusion, the two induced gaps in the PCS measurement are consistent with the three-dimensional bulk state and the two-dimensional surface state superconducting gaps observed in the angle-resolved photoemission spectroscopy (ARPES) measurement.},
doi = {10.1038/s41598-017-07990-3},
journal = {Scientific Reports},
number = 1,
volume = 7,
place = {United States},
year = {2017},
month = {8}
}