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, 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 𝑇c is enhanced to 43.5K for FeSe0.93S0.07, and 41K for FeSe after protonation. Superconducting transitions with 𝑇c 15K for ZrNCl, 7.2K for 1𝑇-TaS2, and 3.8K for Bi2Se3 are induced after protonation. Electric transport in protonated FeSe0.93S0.07 confirms high-temperature superconductivity. Our 1H nuclear magnetic resonance (NMR) measurements on protonated FeSe1−𝑥S𝑥 reveal enhanced spin-lattice relaxation rate 1/1𝑇1 with increasing 𝑥, which is consistent with the LDA calculations that H+ is located in the interstitial sites close to the anions.