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Unveiling the Superconducting Mechanism of Ba 0.51 K 0.49 BiO 3

DOI: 10.1103/PhysRevLett.121.117002 DOI Help

Authors: C. H. P. Wen (Fudan University) , H. C. Xu (Fudan University) , Q. Yao (Fudan University) , R. Peng (Fudan University) , X. H. Niu (Fudan University) , Q. Y. Chen (Science and Technology on Surface Physics and Chemistry Laboratory) , Z. T. Liu (CAS Center for Excellence in Superconducting Electronics (CENSE); Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences) , D. W. Shen (CAS Center for Excellence in Superconducting Electronics (CENSE); Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences) , Q. Song (Fudan University) , X. Lou (Fudan University) , Y. F. Fang (Fudan University) , X. S. Liu (Fudan University) , Y. H. Song (Fudan University) , Y. J. Jiao (Nanjing University; Collaborative Innovation Center of Advanced Microstructures) , T. F. Duan (Nanjing University; Collaborative Innovation Center of Advanced Microstructures) , H. H. Wen (Nanjing University; Collaborative Innovation Center of Advanced Microstructures) , P. Dudin (Diamond Light Source) , G. Kotliar (Rutgers University) , Z. P. Yin (Beijing Normal University) , D. L. Feng (Fudan University; Collaborative Innovation Center of Advanced Microstructures)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Physical Review Letters , VOL 121

State: Published (Approved)
Published: September 2018
Diamond Proposal Number(s): 14737 , 16345 , 20697

Abstract: The mechanism of high superconducting transition temperatures (Tc) in bismuthates remains under debate despite more than 30 years of extensive research. Our angle-resolved photoemission spectroscopy studies on Ba0.51K0.49BiO3 reveal an unexpectedly 34% larger bandwidth than in conventional density functional theory calculations. This can be reproduced by calculations that fully account for long-range Coulomb interactions—the first direct demonstration of bandwidth expansion due to the Fock exchange term, a long-accepted and yet uncorroborated fundamental effect in many body physics.Furthermore, we observe an isotropic superconducting gap with 2Δ0/kBTc=3.51±0.05, and strong electron-phonon interactions with a coupling constant λ∼1.3±0.2. These findings solve a long-standing mystery—Ba0.51K0.49BiO3 is an extraordinary Bardeen-Cooper-Schrieffer superconductor, where long-range Coulomb interactions expand the bandwidth, enhance electron-phonon coupling, and generate the high Tc. Such effects will also be critical for finding new superconductors.

Subject Areas: Physics


Instruments: I05-ARPES

Other Facilities: Advanced Light Source, Shanghai Synchrotron Radiation Facility