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

## TL;DR

This study demonstrates ionic-liquid gating induces protonation in various compounds, significantly enhancing their superconducting transition temperatures and enabling detailed post-gating measurements, revealing insights into proton placement and superconductivity mechanisms.

## Contribution

It introduces a method for protonating multiple materials via ionic-liquid gating, achieving high-temperature superconductivity and enabling post-gating analysis.

## Key findings

- Superconducting transition temperature of FeSe increased to 43.5 K after protonation.
- Protonation induced superconductivity in ZrNCl, 1T-TaS2, and Bi2Se3 with specific T_c values.
- Proton placement near anions confirmed by NMR and theoretical calculations.

## 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.