Experimental evidence of anomalously large superconducting gap on topological surface state of β-Bi2Pd film

Jian Yu Guan; Lingyuan Kong; Li Qin Zhou; Yi Gui Zhong; Hang Li; Hai Jiang Liu; Cen Yao Tang; Da Yu Yan; Fa Zhi Yang; Yao Bo Huang; You Guo Shi; Tian Qian; Hong Ming Weng; Yu Jie Sun; Hong Ding

doi:10.1016/j.scib.2019.07.019

Experimental evidence of anomalously large superconducting gap on topological surface state of β-Bi₂Pd film

Jian Yu Guan
, Lingyuan Kong
, Li Qin Zhou
, Yi Gui Zhong
, Hang Li
, Hai Jiang Liu
, Cen Yao Tang
, Da Yu Yan
, Fa Zhi Yang
, Yao Bo Huang
, You Guo Shi
, Tian Qian
, Hong Ming Weng
, Yu Jie Sun
, Hong Ding

Research output: Contribution to journal › Article › peer-review

20 Scopus citations

Abstract

Connate topological superconductor (TSC) combines topological surface states with nodeless superconductivity in a single material, achieving effective p-wave pairing without interface complication. By combining angle-resolved photoemission spectroscopy and in-situ molecular beam epitaxy, we studied the momentum-resolved superconductivity in β-Bi₂Pd film. We found that the superconducting gap of topological surface state (Δ_TSS ∼ 3.8 meV) is anomalously enhanced from its bulk value (Δ_b ∼ 0.8 meV). The ratio of 2Δ_TSS/k_BT_c ∼ 16.3, is substantially larger than the BCS value. By measuring β-Bi₂Pd bulk single crystal as a comparison, we clearly observed the upward-shift of chemical potential in the film. In addition, a concomitant increasing of surface weight on the topological surface state was revealed by our first principle calculation, suggesting that the Dirac-fermion-mediated parity mixing may cause this anomalous superconducting enhancement. Our results establish β-Bi₂Pd film as a unique case of connate TSCs with a highly enhanced topological superconducting gap, which may stabilize Majorana zero modes at a higher temperature.

Original language	English
Pages (from-to)	1215-1221
Number of pages	7
Journal	Science Bulletin
Volume	64
Issue number	17
DOIs	https://doi.org/10.1016/j.scib.2019.07.019
State	Published - Sep 15 2019
Externally published	Yes

Funding

This work at IOP was supported by the Ministry of Science and Technology of China , China ( 2016YFA0401000 , 2016YFA0300600 , 2015CB921000 ), the National Natural Science Foundation of China , China ( 11888101 , 11574371 , 11622435 , 11474340 and 11774399 ), the Chinese Academy of Sciences, China ( XDB28000000 , XDB07000000 , QYZDB-SSW-SLH043 ), the Beijing Municipal Science and Technology Commission, China ( Z171100002017018 , Z181100004218005 and Z171100002017018 ), Beijing Natural Science Foundation (Z180008), and the National Key Research and Development Program of China , China ( 2017YFA0302901 ), Y.-B. H. acknowledges supports by the Ministry of Science and Technology of China, China ( 2016YFA0401002 ) and the CAS Pioneer “Hundred Talents Program” (type C). The authors also thank C. Fang for useful discussions. This work at IOP was supported by the Ministry of Science and Technology of China, China (2016YFA0401000, 2016YFA0300600, 2015CB921000), the National Natural Science Foundation of China, China (11888101, 11574371, 11622435, 11474340 and 11774399), the Chinese Academy of Sciences, China (XDB28000000, XDB07000000, QYZDB-SSW-SLH043), the Beijing Municipal Science and Technology Commission, China (Z171100002017018, Z181100004218005 and Z171100002017018), Beijing Natural Science Foundation (Z180008), and the National Key Research and Development Program of China, China (2017YFA0302901), Y.-B. H. acknowledges supports by the Ministry of Science and Technology of China, China (2016YFA0401002) and the CAS Pioneer ?Hundred Talents Program? (type C). The authors also thank C. Fang for useful discussions. H.D. and Y.-J. S. designed the experiments and supervised the project. J.-Y. G. and Y.-J. S. grew the thin films and performed STM, RHEED and XRD measurements. L.-Y. K. and J.-Y. G. performed ARPES measurements with the assistance of H. Li. Y.-G. Z. H.-J. L. C.-Y. T. F.-Z. Y. Y.-B. H. and T. Q. D.-Y. Y. and Y.-G. S. provided high quality bulk single crystals. L.-Q. Z. and H.-M. W. performed first principle calculation. J.-Y. G. and L.-Y. K. analysed the ARPES data. J.-Y. G. plotted the figures. L.-Y. K. J.-Y. G. Y.-J. S. and H. D. wrote the manuscripts with inputs from all the authors.

Keywords

Multiband superconductivity
Photoemission spectroscopy
Thin film
Topological surface state

Access to Document

10.1016/j.scib.2019.07.019

Cite this

Guan, J. Y., Kong, L., Zhou, L. Q., Zhong, Y. G., Li, H., Liu, H. J., Tang, C. Y., Yan, D. Y., Yang, F. Z., Huang, Y. B., Shi, Y. G., Qian, T., Weng, H. M., Sun, Y. J., & Ding, H. (2019). Experimental evidence of anomalously large superconducting gap on topological surface state of β-Bi₂Pd film. Science Bulletin, 64(17), 1215-1221. https://doi.org/10.1016/j.scib.2019.07.019

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abstract = "Connate topological superconductor (TSC) combines topological surface states with nodeless superconductivity in a single material, achieving effective p-wave pairing without interface complication. By combining angle-resolved photoemission spectroscopy and in-situ molecular beam epitaxy, we studied the momentum-resolved superconductivity in β-Bi2Pd film. We found that the superconducting gap of topological surface state (ΔTSS ∼ 3.8 meV) is anomalously enhanced from its bulk value (Δb ∼ 0.8 meV). The ratio of 2ΔTSS/kBTc ∼ 16.3, is substantially larger than the BCS value. By measuring β-Bi2Pd bulk single crystal as a comparison, we clearly observed the upward-shift of chemical potential in the film. In addition, a concomitant increasing of surface weight on the topological surface state was revealed by our first principle calculation, suggesting that the Dirac-fermion-mediated parity mixing may cause this anomalous superconducting enhancement. Our results establish β-Bi2Pd film as a unique case of connate TSCs with a highly enhanced topological superconducting gap, which may stabilize Majorana zero modes at a higher temperature.",

keywords = "Multiband superconductivity, Photoemission spectroscopy, Thin film, Topological surface state",

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AU - Kong, Lingyuan

AU - Zhou, Li Qin

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AU - Li, Hang

AU - Liu, Hai Jiang

AU - Tang, Cen Yao

AU - Yan, Da Yu

AU - Yang, Fa Zhi

AU - Huang, Yao Bo

AU - Shi, You Guo

AU - Qian, Tian

AU - Weng, Hong Ming

AU - Sun, Yu Jie

AU - Ding, Hong

PY - 2019/9/15

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N2 - Connate topological superconductor (TSC) combines topological surface states with nodeless superconductivity in a single material, achieving effective p-wave pairing without interface complication. By combining angle-resolved photoemission spectroscopy and in-situ molecular beam epitaxy, we studied the momentum-resolved superconductivity in β-Bi2Pd film. We found that the superconducting gap of topological surface state (ΔTSS ∼ 3.8 meV) is anomalously enhanced from its bulk value (Δb ∼ 0.8 meV). The ratio of 2ΔTSS/kBTc ∼ 16.3, is substantially larger than the BCS value. By measuring β-Bi2Pd bulk single crystal as a comparison, we clearly observed the upward-shift of chemical potential in the film. In addition, a concomitant increasing of surface weight on the topological surface state was revealed by our first principle calculation, suggesting that the Dirac-fermion-mediated parity mixing may cause this anomalous superconducting enhancement. Our results establish β-Bi2Pd film as a unique case of connate TSCs with a highly enhanced topological superconducting gap, which may stabilize Majorana zero modes at a higher temperature.

AB - Connate topological superconductor (TSC) combines topological surface states with nodeless superconductivity in a single material, achieving effective p-wave pairing without interface complication. By combining angle-resolved photoemission spectroscopy and in-situ molecular beam epitaxy, we studied the momentum-resolved superconductivity in β-Bi2Pd film. We found that the superconducting gap of topological surface state (ΔTSS ∼ 3.8 meV) is anomalously enhanced from its bulk value (Δb ∼ 0.8 meV). The ratio of 2ΔTSS/kBTc ∼ 16.3, is substantially larger than the BCS value. By measuring β-Bi2Pd bulk single crystal as a comparison, we clearly observed the upward-shift of chemical potential in the film. In addition, a concomitant increasing of surface weight on the topological surface state was revealed by our first principle calculation, suggesting that the Dirac-fermion-mediated parity mixing may cause this anomalous superconducting enhancement. Our results establish β-Bi2Pd film as a unique case of connate TSCs with a highly enhanced topological superconducting gap, which may stabilize Majorana zero modes at a higher temperature.

KW - Multiband superconductivity

KW - Photoemission spectroscopy

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