Phase Diagram and High Temperature Superconductivity at 65 K in Tuning Carrier Concentration of Single-Layer FeSe Films

TL;DR

This study maps the phase diagram of single-layer FeSe films on SrTiO3, revealing a high-temperature superconducting phase at 65 K achieved through annealing, with significant changes in electronic structure.

Contribution

It introduces a method to tune carrier concentration in FeSe films via annealing, leading to the discovery of a high-Tc superconducting phase and detailed phase diagram.

Findings

Superconductivity at ~65 K achieved in single-layer FeSe films.

Significant band structure and Fermi surface changes observed.

Identification of two competing phases during annealing.

Abstract

Superconductivity in the cuprate superconductors and the Fe-based superconductors is realized by doping the parent compound with charge carriers, or by application of high pressure, to suppress the antiferromagnetic state. Such a rich phase diagram is important in understanding superconductivity mechanism and other physics in the Cu- and Fe-based high temperature superconductors. In this paper, we report a phase diagram in the single-layer FeSe films grown on SrTiO3 substrate by an annealing procedure to tune the charge carrier concentration over a wide range. A dramatic change of the band structure and Fermi surface is observed, with two distinct phases identified that are competing during the annealing process. Superconductivity with a record high transition temperature (Tc) at ~65 K is realized by optimizing the annealing process. The wide tunability of the system across different phases, and its high-Tc, make the single-layer FeSe film ideal not only to investigate the superconductivity physics and mechanism, but also to study novel quantum phenomena and for potential applications.