Ionic-liquid-gating induced protonation and superconductivity in FeSe, FeSe0.93S0.07, ZrNCl, 1T-TaS2, and Bi2Se3

Abstract

We report protonation in several compounds by an ionic-liquid-gating method, with optimized gating conditions. This leads to single superconducting phases for several compounds. Non-volatility of protons allow post-gating magnetization and transport measurements. The superconducting transition temperature \(T_C\) is enhanced to 43.5~K for FeSe\(_{0.93}\)S\(_{0.07}\), and 41~K for FeSe after protonation. Superconductivity with \(T_c\)$\approx\(15~K for ZrNCl, \)\approx\(7.2~K for 1\)T\(-TaS\)_2\(, and \)\approx\(3.8~K for Bi\)_2\(Se\)_3\( are induced after protonation. Electric transport in protonated FeSe\)_{0.93}\(S\)_{0.07}\( confirms high-temperature superconductivity. Our \)^{1}\(H NMR measurements on protonated FeSe\)_{1-x}\(S\)_{x}\( reveal enhanced spin-lattice relaxation rate \)1/^{1}T_1\( with increasing \)x\(, which is consistent with LDA calculations that H\)^{+}$ are located in the interstitial sites close to the anions.