We report the first observation of a pressure-induced transition from a superconducting (SC) to an insulating (I) phase in single-crystal Ba1-xKxBiO3 (x = 0.4, 0.43, 0.52, and 0.58) superconductors. X-ray diffraction measurements conducted at 20 K reveal a direct relationship between this SC-I transition and a pressure-induced distortion of crystal structure. With increasing pressure, the lattice parameters a and c of the ambient-pressure superconducting tetragonal (T) phase are compressed continuously below a critical pressure (Pc1), wherein the pressure (P) dependence of superconducting transition temperature (Tc) displays a small variation. However, upon further compression, the lattice of the compressed T phase displays an anisotropic change, and Tc shows a monotonous decrease. When the pressure reaches Pc2 (Pc2 > Pc1), the compressed T phase collapses along the c axis, followed by the disappearance of superconductivity and the appearance of the insulating phase. This SC-I transition is fully reversible, with the critical pressure increasing alongside K doping concentration. These findings are strikingly similar to the SC-I transition observed in hole-doped high-Tc cuprate superconductors under pressure. Identifying their commonalities could deepen our understanding of the mechanisms that underlie high- Tc superconductivity in these two oxide superconductors with a perovskite structure.
@article{arxiv.2305.08406,
title = {Superconducting-insulating phase transition in pressurized Ba1-xKxBiO3},
author = {Jinyu Han and Xiangde Zhu and Jianfeng Zhang and Shu Cai and Luhong Wang and Yang Gao and Fuyang Liu and Haozhe Liu and Saori I. Kawaguchi and Jing Guo and Yazhou Zhou and Jinyu Zhao and Pengyu Wang and Lixin Cao and Mingliang Tian and Qi Wu and Tao Xiang and Liling Sun},
journal= {arXiv preprint arXiv:2305.08406},
year = {2025}
}