Tuning phase transitions of FeSe thin flakes by field effect transistor with solid ion conductor as gate dielectric

TL;DR

This study introduces a solid ion conductor-based FET device to precisely tune carrier density in FeSe thin flakes, enabling control over phase transitions and achieving high-temperature superconductivity with a dome-shaped phase diagram.

Contribution

It demonstrates a novel SIC-FET device that allows high doping levels and stabilization of new phases in FeSe, surpassing traditional gating methods.

Findings

Achieved a superconducting transition temperature of 46.6 K at optimal doping.

Mapped out a dome-shaped superconducting phase diagram with increasing Li content.

Revealed the ability to stabilize novel structural phases inaccessible by conventional means.

Abstract

We develop a novel field effect transistor (FET) device using solid ion conductor (SIC) as a gate dielectric, and we can tune the carrier density of FeSe by driving lithium ions in and out of the FeSe thin flakes, and consequently control the material properties and its phase transitions. A dome-shaped superconducting phase diagram was mapped out with increasing Li content, with $T_c$ $\sim$ 46.6 K for the optimal doping, and an insulating phase was reached at the extremely overdoped regime. Our study suggests that, using solid ion conductor as a gate dielectric, the SIC-FET device can achieve much higher carrier doping in the bulk, and suit many surface sensitive experimental probes, and can stabilize novel structural phases that are inaccessible in ordinary conditions.