Temperature Evolution of Energy Gap and Band Structure in the Superconducting and Pseudogap States of Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ Superconductor Revealed by Laser-Based Angle-Resolved Photoemission Spectroscopy
1National Laboratory for Superconductivity, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 2University of Chinese Academy of Sciences, Beijing 100049 3Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA 4Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 5Collaborative Innovation Center of Quantum Matter, Beijing 100871
Abstract：We carry out detailed momentum-dependent and temperature-dependent measurements on Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ (Bi2212) superconductor in the superconducting and pseudogap states by super-high resolution laser-based angle-resolved photoemission spectroscopy. The precise determination of the superconducting gap for the nearly optimally doped Bi2212 ($T_{\rm c}=91$ K) at low temperature indicates that the momentum-dependence of the superconducting gap deviates from the standard $d$-wave form ($\cos(2{\it \Phi}$)). It can be alternatively fitted by including a high-order term ($\cos(6{\it \Phi}$)) in which the next nearest-neighbor interaction is considered. We find that the band structure near the antinodal region smoothly evolves across the pseudogap temperature without a signature of band reorganization which is distinct from that found in Bi$_2$Sr$_2$CuO$_{6+\delta}$ superconductors. This indicates that the band reorganization across the pseudogap temperature is not a universal behavior in cuprate superconductors. These results provide new insights in understanding the nature of the superconducting gap and pseudogap in high-temperature cuprate superconductors.
. [J]. 中国物理快报, 2018, 35(1): 17401-.
Xuan Sun, Wen-Tao Zhang, Lin Zhao, Guo-Dong Liu, Gen-Da Gu, Qin-Jun Peng, Zhi-Min Wang, Shen-Jin Zhang, Feng Yang, Chuang-Tian Chen, Zu-Yan Xu, Xing-Jiang Zhou. Temperature Evolution of Energy Gap and Band Structure in the Superconducting and Pseudogap States of Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ Superconductor Revealed by Laser-Based Angle-Resolved Photoemission Spectroscopy. Chin. Phys. Lett., 2018, 35(1): 17401-.
2018, Vol. 35 
