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

摘要

Superconductivity in the cuprate superconductors and the Fe-basedsuperconductors 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 superconductivitymechanism and other physics in the Cu- and Fe-based high temperaturesuperconductors. In this paper, we report a phase diagram in the single-layerFeSe films grown on SrTiO3 substrate by an annealing procedure to tune thecharge carrier concentration over a wide range. A dramatic change of the bandstructure and Fermi surface is observed, with two distinct phases identifiedthat are competing during the annealing process. Superconductivity with arecord high transition temperature (Tc) at ~65 K is realized by optimizing theannealing process. The wide tunability of the system across different phases,and its high-Tc, make the single-layer FeSe film ideal not only to investigatethe superconductivity physics and mechanism, but also to study novel quantumphenomena and for potential applications.