Directly visualizing the sign change of d-wave superconducting gap in Bi2Sr2CaCu2O8+δ by phase-referenced quasiparticle interference

Qiangqiang Gu; Siyuan Wan; Qingkun Tang; Zengyi Du; Huan Yang; Qiang-Hua Wang; Ruidan Zhong; Jinsheng Wen; G D Gu; Hai-Hu Wen

doi:10.1038/s41467-019-09340-5

Directly visualizing the sign change of d-wave superconducting gap in Bi₂Sr₂CaCu₂O_8+δ by phase-referenced quasiparticle interference

Nat Commun. 2019 Apr 8;10(1):1603. doi: 10.1038/s41467-019-09340-5.

Authors

Qiangqiang Gu¹, Siyuan Wan¹, Qingkun Tang¹, Zengyi Du¹, Huan Yang², Qiang-Hua Wang³, Ruidan Zhong⁴, Jinsheng Wen⁴, G D Gu⁴, Hai-Hu Wen⁵

Affiliations

¹ National Laboratory of Solid State Microstructures and Department of Physics, Center for Superconducting Physics and Materials, Collaborative Innovation Center for Advanced Microstructures, Nanjing University, 210093, Nanjing, China.
² National Laboratory of Solid State Microstructures and Department of Physics, Center for Superconducting Physics and Materials, Collaborative Innovation Center for Advanced Microstructures, Nanjing University, 210093, Nanjing, China. huanyang@nju.edu.cn.
³ National Laboratory of Solid State Microstructures and Department of Physics, Center for Superconducting Physics and Materials, Collaborative Innovation Center for Advanced Microstructures, Nanjing University, 210093, Nanjing, China. qhwang@nju.edu.cn.
⁴ Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York, 11973, USA.
⁵ National Laboratory of Solid State Microstructures and Department of Physics, Center for Superconducting Physics and Materials, Collaborative Innovation Center for Advanced Microstructures, Nanjing University, 210093, Nanjing, China. hhwen@nju.edu.cn.

Abstract

The superconducting state is formed by the condensation of Cooper pairs and protected by the superconducting gap. The pairing interaction between the two electrons of a Cooper pair determines the gap function. Thus, it is pivotal to detect the gap structure for understanding the mechanism of superconductivity. In cuprate superconductors, it has been well established that the gap may have a d-wave function. This gap function has an alternative sign change in the momentum space. It is however hard to visualize this sign change. Here we report the measurements of scanning tunneling spectroscopy in Bi₂Sr₂CaCu₂O_8+δ and conduct the analysis of phase-referenced quasiparticle interference (QPI). We see the seven basic scattering vectors that connect the octet ends of the banana-shaped contour of Fermi surface. The phase-referenced QPI clearly visualizes the sign change of the d-wave gap. Our results illustrate an effective way for determining the sign change of unconventional superconductors.

Publication types

Research Support, Non-U.S. Gov't