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

Wenqing Dai, Anthony Raymond Richardella, Renzhong Du, Weiwei Zhao, Xin Liu, Chaoxing Liu, Song Hsun Huang, Raman Sankar, Fangcheng Chou, Nitin Samarth, Qi Li

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Abstract

Proximity-effect-induced superconductivity was studied in epitaxial topological insulator Bi 2 Se 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 2 Se 3 was observed in the spectra, which decreased with increasing Bi 2 Se 3 layer thickness, consistent with the proximity effect in the bulk states of Bi 2 Se 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 2 Se 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 2 Se 3 layer thickness, but the ratio between the second gap and the bulk state gap remained about the same for different Bi 2 Se 3 thicknesses. It is plausible that this is due to superconductivity in Bi 2 Se 3 topological surface states induced through the bulk states. 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.

Original languageEnglish (US)
Article number7631
JournalScientific reports
Volume7
Issue number1
DOIs
StatePublished - Dec 1 2017

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Spectrum Analysis
Photoelectron Spectroscopy
Temperature
Superconductivity

All Science Journal Classification (ASJC) codes

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Cite this

@article{63d8f2978d7c40f5a88cf18e1c9cde28,
title = "Proximity-effect-induced Superconducting Gap in Topological Surface States - A Point Contact Spectroscopy Study of NbSe 2 /Bi 2 Se 3 Superconductor-Topological Insulator Heterostructures",
abstract = "Proximity-effect-induced superconductivity was studied in epitaxial topological insulator Bi 2 Se 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 2 Se 3 was observed in the spectra, which decreased with increasing Bi 2 Se 3 layer thickness, consistent with the proximity effect in the bulk states of Bi 2 Se 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 2 Se 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 2 Se 3 layer thickness, but the ratio between the second gap and the bulk state gap remained about the same for different Bi 2 Se 3 thicknesses. It is plausible that this is due to superconductivity in Bi 2 Se 3 topological surface states induced through the bulk states. 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.",
author = "Wenqing Dai and Richardella, {Anthony Raymond} and Renzhong Du and Weiwei Zhao and Xin Liu and Chaoxing Liu and Huang, {Song Hsun} and Raman Sankar and Fangcheng Chou and Nitin Samarth and Qi Li",
year = "2017",
month = "12",
day = "1",
doi = "10.1038/s41598-017-07990-3",
language = "English (US)",
volume = "7",
journal = "Scientific Reports",
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Proximity-effect-induced Superconducting Gap in Topological Surface States - A Point Contact Spectroscopy Study of NbSe 2 /Bi 2 Se 3 Superconductor-Topological Insulator Heterostructures . / Dai, Wenqing; Richardella, Anthony Raymond; Du, Renzhong; Zhao, Weiwei; Liu, Xin; Liu, Chaoxing; Huang, Song Hsun; Sankar, Raman; Chou, Fangcheng; Samarth, Nitin; Li, Qi.

In: Scientific reports, Vol. 7, No. 1, 7631, 01.12.2017.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Proximity-effect-induced Superconducting Gap in Topological Surface States - A Point Contact Spectroscopy Study of NbSe 2 /Bi 2 Se 3 Superconductor-Topological Insulator Heterostructures

AU - Dai, Wenqing

AU - Richardella, Anthony Raymond

AU - Du, Renzhong

AU - Zhao, Weiwei

AU - Liu, Xin

AU - Liu, Chaoxing

AU - Huang, Song Hsun

AU - Sankar, Raman

AU - Chou, Fangcheng

AU - Samarth, Nitin

AU - Li, Qi

PY - 2017/12/1

Y1 - 2017/12/1

N2 - Proximity-effect-induced superconductivity was studied in epitaxial topological insulator Bi 2 Se 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 2 Se 3 was observed in the spectra, which decreased with increasing Bi 2 Se 3 layer thickness, consistent with the proximity effect in the bulk states of Bi 2 Se 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 2 Se 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 2 Se 3 layer thickness, but the ratio between the second gap and the bulk state gap remained about the same for different Bi 2 Se 3 thicknesses. It is plausible that this is due to superconductivity in Bi 2 Se 3 topological surface states induced through the bulk states. 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.

AB - Proximity-effect-induced superconductivity was studied in epitaxial topological insulator Bi 2 Se 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 2 Se 3 was observed in the spectra, which decreased with increasing Bi 2 Se 3 layer thickness, consistent with the proximity effect in the bulk states of Bi 2 Se 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 2 Se 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 2 Se 3 layer thickness, but the ratio between the second gap and the bulk state gap remained about the same for different Bi 2 Se 3 thicknesses. It is plausible that this is due to superconductivity in Bi 2 Se 3 topological surface states induced through the bulk states. 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.

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ER -