The superconducting transition temperature, Tc, of FeSe can be significantly enhanced several-fold by applying pressure, electron doping, intercalating spacing layer, and reducing dimensionality. Various ordered electronic phases, such as nematicity and spin density waves, have also been observed accompanying high-Tc superconductivity. Investigation on the evolution of the electronic structure with Tc is essential to understanding electronic behavior and high-Tc superconductivity in FeSe and its derived superconductors. In this report, we have found a series of discrete superconducting phases, with a maximum Tc up to 44 K, in H+-intercalated FeSe single crystals using an ionic liquid gating method. Accompanied with the increase of Tc, suppression of the nematic phase and evolution from non-Fermi-liquid to Fermi-liquid behavior was observed. An abrupt change in the Fermi surface topology was proposed to explain the discrete superconducting phases. A band structure that favors the high-Tc superconducting phase was also revealed.
@article{arxiv.2112.12902,
title = {Protonation-induced discrete superconducting phases in bulk FeSe single crystals},
author = {Yan Meng and Xiangzhuo Xing and Xiaolei Yi and Bin Li and Nan Zhou and Meng Li and Yufeng Zhang and Wei Wei and Jiajia Feng and Kensei Terashima and Yoshihiko Takano and Yue Sun and Zhixiang Shi},
journal= {arXiv preprint arXiv:2112.12902},
year = {2022}
}