Band structure and charge doping effects of potassium-adsorbed FeSe/SrTiO3 system

TL;DR

This study uses theoretical methods to analyze how potassium adsorption affects the electronic structure and charge doping in FeSe/SrTiO3 films, providing insights into their superconducting properties.

Contribution

It offers a detailed theoretical analysis of potassium-induced charge doping and band structure modifications in FeSe thin films, aiding future experimental and theoretical research.

Findings

Potassium efficiently dopes electrons to the top layer FeSe.

Electron pockets appear at M point with moderate K coverage.

Heavy doping can induce electron pockets at Γ point, influencing superconductivity.

Abstract

We theoretically study, through combining the density functional theory and an unfolding technique, the electronic band structure and the charge doping effects for the deposition of potassium (K) on multilayer FeSe films grown on SrTiO3 (001) surface. These results form a theoretical base line for further detailed studies of low-temperature electronic properties and their multiway quantum engineering of FeSe thin films. We explain the Fermi surface topology observed in experiment and formulate the amount of doped electrons as a function of atomic K coverage. We show that the atomic K deposition efficiently dopes electrons to top layer FeSe. Both checkerboard and pair-checkerboard antiferromagnetic (AFM) FeSe layers show electron pockets at M point and no Fermi pocket at $\Gamma$ point with moderate atomic K coverage. The electron transfer from K adsorbate to FeSe film introduces a strong electric field, which leads to a double-Weyl cone structure at M point in the Brillouin zone of checkerboard-AFM FeSe. We demonstrate that with experimentally accessible heavy electron doping, an electron-like Fermi pocket will emerge at $\Gamma$ point, which should manifest itself in modulating the high-temperature superconductivity of FeSe thin films.