Protonation induced high-T_c phases in iron-based superconductors evidenced by NMR and magnetization measurements
Yi Cui;Gehui Zhang;Haobo Li;Hai Lin;Xiyu Zhu;Hai-Hu Wen;Guoqing Wang;Jinzhao Sun;Mingwei Ma;Yuan Li;Dongliang Gong;Tao Xie;Yanhong Gu;Shiliang Lie;Huiqian Luo;Pu Yu;Weiqiang Yu;Department of Physics, Renmin University of China;State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University;Center for Superconducting Physics and Materials, National Laboratory of Solid State Microstructures and Department of Physics, Collaborative Innovation Center for Advanced Microstructures, Nanjing University;International Center for Quantum Materials, School of Physics, Peking University;Collaborative Innovation Center of Quantum Matter;Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences;University of Chinese Academy of Sciences;
Chemical substitution during growth is a well-established method to manipulate electronic states of quantum materials, and leads to rich spectra of phase diagrams in cuprate and iron-based superconductors. Here we report a novel and generic strategy to achieve nonvolatile electron doping in series of(i.e.11 and 122 structures) Fe-based superconductors by ionic liquid gating induced protonation at room temperature. Accumulation of protons in bulk compounds induces superconductivity in the parent compounds, and enhances the Tclargely in some superconducting ones. Furthermore, the existence of proton in the lattice enables the first proton nuclear magnetic resonance(NMR) study to probe directly superconductivity. Using Fe S as a model system, our NMR study reveals an emergent high-Tcphase with no coherence peak which is hard to measure by NMR with other isotopes. This novel electric-fieldinduced proton evolution opens up an avenue for manipulation of competing electronic states(e.g.Mott insulators), and may provide an innovative way for a broad perspective of NMR measurements with greatly enhanced detecting resolution.