1School of Mathematics and Physics, North China Electric Power University, Beijing 102206 2Department of Physics, and Beijing Key Laboratory of Opto-electronic Functional Materials & Micro-nano Devices, Renmin University, Beijing 100872 3International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871 4National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 5Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA 6Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190 7Collaborative Innovation Center of Quantum Matter, Beijing 100871 8Innovative Center for Advanced Microstructures, Nanjing University, Nanjing 210093 9State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084
Abstract：We report protonation in several compounds by an ionic-liquid-gating method, under optimized gating conditions. This leads to single superconducting phases for several compounds. Non-volatility of protons allows post-gating magnetization and transport measurements. The superconducting transition temperature $T_{\rm c}$ is enhanced to 43.5 K for FeSe$_{0.93}$S$_{0.07}$, and 41 K for FeSe after protonation. Superconducting transitions with $T_{\rm c} \sim 15$ K for ZrNCl, $\sim$7.2 K for 1$T$-TaS$_2$, and $\sim$3.8 K for Bi$_2$Se$_3$ are induced after protonation. Electric transport in protonated FeSe$_{0.93}$S$_{0.07}$ confirms high-temperature superconductivity. Our $^{1}$H nuclear magnetic resonance (NMR) measurements on protonated FeSe$_{1-x}$S$_{x}$ reveal enhanced spin-lattice relaxation rate $1/^{1}T_1$ with increasing $x$, which is consistent with the LDA calculations that H$^{+}$ is located in the interstitial sites close to the anions.
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2019, Vol. 36 
