Interface induced states at the boundary between a 3D topological insulator Bi$_2$Se$_3$ and a ferromagnetic insulator EuS

TL;DR

This study uses relativistic DFT calculations to analyze the electronic structure of Bi$_2$Se$_3$ thin films on EuS, revealing a hybridization-controlled gap and Eu doping effects on magnetization.

Contribution

It provides new insights into the interface states and magnetic properties of Bi$_2$Se$_3$/EuS heterostructures, highlighting the role of film thickness and Eu doping.

Findings

The topological gap is hybridization-controlled and depends on film thickness.

Eu doping induces significant magnetic moments on neighboring atoms.

Magnetic contribution to the gap is negligible.

Abstract

By means of relativistic density functional theory (DFT) calculations we study electron band structure of the topological insulator (TI) Bi$_2$Se$_3$ thin films deposited on the ferromagnetic insulator (FMI) EuS substrate. In the Bi$_2$Se$_3$/EuS heterostructure, the gap opened in the spectrum of the topological state has a hybridization character and is shown to be controlled by the Bi$_2$Se$_3$ film thickness, while magnetic contribution to the gap is negligibly small. We also analyzed the effect of Eu doping on the magnetization of the Bi$_2$Se$_3$ film and demonstrated that the Eu impurity induces magnetic moments on neighboring Se and Bi atoms an order of magnitude larger than the substrate-induced moments. Recent magnetic and magneto-transport measurements in EuS/Bi$_2$Se$_3$ heterostructure are discussed.