Electronic origin of high-temperaturesuperconductivity in single-layer FeSesuperconductor

摘要

The recent discovery of high-temperature superconductivity in iron-based compounds hasattracted much attention . How to further increase the superconducting transition temperature( Tc ) and how to understand the superconductivity mechanism are two prominent issues facingthe current study of iron-based superconductors. The latest report of high- Tc superconductivity in a single-layer FeSe is therefore both surprising and significant. Here we present investigations of the electronic structure and superconducting gap of the single-layer FeSe superconductor. Its Fermi surface is distinct from other iron-based superconductors, consisting only of electron-likepockets near the zone corner without indication of any Fermi surface around the zone centre.Nearly isotropic superconducting gap is observed in this strictly two-dimensional system. Thetemperature dependence of the superconducting gap gives a transition temperature Tc-55 K. These results have established a clear case that such a simple electronic structure is compatiblewith high- Tc superconductivity in iron-based superconductors.