Discovery of a high-temperature antiferromagnetic state and transport signatures of exchange interactions in a Bi2Se3/EuSe heterostructure

TL;DR

This study demonstrates a high-temperature antiferromagnetic state at the Bi2Se3/EuSe interface, revealing exchange interactions that influence topological surface states and transport properties, with implications for spintronics and quantum devices.

Contribution

It provides experimental evidence of exchange interactions inducing an antiferromagnetic state in a topological insulator/magnetic insulator heterostructure at high temperatures.

Findings

Reduction of in-plane magnetic susceptibility at the interface

Formation of an antiferromagnetic layer with elevated Neel temperature

Interfacial exchange coupling affects transport in topological surface states

Abstract

Spatial confinement of electronic topological surface states (TSS) in topological insulators poses a formidable challenge because TSS are protected by time-reversal symmetry. In previous works formation of a gap in the electronic spectrum of TSS has been successfully demonstrated in topological insulator/magnetic material heterostructures, where ferromagnetic exchange interactions locally lifts the time-reversal symmetry. Here we report an experimental evidence of exchange interaction between a topological insulator Bi2Se3 and a magnetic insulator EuSe. Spin-polarized neutron reflectometry reveals a reduction of the in-plane magnetic susceptibility within a 2 nm interfacial layer of EuSe, and the combination of SQUID magnetometry and Hall measurements points to the formation of an antiferromagnetic layer with at least five-fold enhancement of N\'eel's temperature. Abrupt resistance changes in high magnetic fields indicate interfacial exchange coupling that affects transport in a TSS. High temperature local control of TSS with zero net magnetization unlocks new opportunities for the design of electronic, spintronic and quantum computation devices, ranging from quantization of Hall conductance in zero fields to spatial localization of non-Abelian excitations in superconducting topological qubits.