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

作　　者：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 

机构地区：[1]Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China [2]School o f Physics, University of Chinese Academy of Sciences, Beijing 100190, China [3]Shanghai Synchrotron Radiation Facility, Shanghai Institute o f Applied Physics, Chinese Academy of Sciences, Shanghai 201204, China [4]CAS Center for Excellence in Topological Quantum Computation, University o f Chinese Academy of Sciences, Beijing 100190, China [5]Songshan Lake Materials Laboratory, Dongguan 523808, China

出　　处：《Science Bulletin》2019年第17期1215-1221,共7页科学通报（英文版）

基　　金：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);the National Key Research and Development Program of China, China (2017YFA0302901);supports by the Ministry of Science and Technology of China, China (2016YFA0401002);the CAS Pioneer ‘‘Hundred Talents Program” (type C)

摘　　要：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 b-Bi2 Pd film. We found that the superconducting gap of topological surface state(DTSS$ 3.8 meV) is anomalously enhanced from its bulk value(Db$ 0.8 meV). The ratio of 2 DTSS/kBTc$ 16.3, is substantially larger than the BCS value. By measuring b-Bi2 Pd 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 b-Bi2 Pd 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.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 b-Bi2 Pd film. We found that the superconducting gap of topological surface state(DTSS$ 3.8 meV) is anomalously enhanced from its bulk value(Db$ 0.8 meV). The ratio of 2 DTSS/kBTc$ 16.3, is substantially larger than the BCS value. By measuring b-Bi2 Pd 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 b-Bi2 Pd 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.

关 键 词：TOPOLOGICAL surface state MULTIBAND SUPERCONDUCTIVITY THIN film PHOTOEMISSION spectroscopy 

分 类 号：N[自然科学总论]