Electronic Structures of the Superconducting Single-Layer FeSe/SrTiO $$_3$$ 3 Films

Abstract

Much attention has been attracted by the recent discovery of iron-based high-temperature superconductors. Nevertheless, two prominent issues are yet to be addressed. The first one is to find out a way to further increase the superconducting transition temperature (\(\mathrm{T}_c\)) in iron-based superconductors, and the second one is to understand the superconductivity mechanism. Recently, possible high \(\mathrm{T}_c\) superconductivity has been reported in a single-layer FeSe/SrTiO\(_3\) film. The observation of a high transition temperature in a material with the simplest crystal structure provides an ideal platform to study the above important issues. We have performed 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-like pockets near the zone corner without indication of any Fermi surface around the zone center. The superconducting gap is nearly isotropic, and the temperature dependence of the superconducting gap gives a transition temperature \(\mathrm{T}_c\sim 55\) K for this superconducting film. Our results have established a clear case that high \(\mathrm{T}_c\) superconductivity in iron-based superconductors can be realized with such a simple electronic structure.