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Quantum Phase Transition of Correlated Iron-Based Superconductivity in LiFe_{1-x}Co_{x}As.

  • Author(s): Yin, Jia-Xin
  • Zhang, Songtian S
  • Dai, Guangyang
  • Zhao, Yuanyuan
  • Kreisel, Andreas
  • Macam, Gennevieve
  • Wu, Xianxin
  • Miao, Hu
  • Huang, Zhi-Quan
  • Martiny, Johannes HJ
  • Andersen, Brian M
  • Shumiya, Nana
  • Multer, Daniel
  • Litskevich, Maksim
  • Cheng, Zijia
  • Yang, Xian
  • Cochran, Tyler A
  • Chang, Guoqing
  • Belopolski, Ilya
  • Xing, Lingyi
  • Wang, Xiancheng
  • Gao, Yi
  • Chuang, Feng-Chuan
  • Lin, Hsin
  • Wang, Ziqiang
  • Jin, Changqing
  • Bang, Yunkyu
  • Hasan, M Zahid
  • et al.
Abstract

The interplay between unconventional Cooper pairing and quantum states associated with atomic scale defects is a frontier of research with many open questions. So far, only a few of the high-temperature superconductors allow this intricate physics to be studied in a widely tunable way. We use scanning tunneling microscopy to image the electronic impact of Co atoms on the ground state of the LiFe_{1-x}Co_{x}As system. We observe that impurities progressively suppress the global superconducting gap and introduce low energy states near the gap edge, with the superconductivity remaining in the strong-coupling limit. Unexpectedly, the fully opened gap evolves into a nodal state before the Cooper pair coherence is fully destroyed. Our systematic theoretical analysis shows that these new observations can be quantitatively understood by the nonmagnetic Born-limit scattering effect in an s±-wave superconductor, unveiling the driving force of the superconductor to metal quantum phase transition.

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