Transport measurement of ferromagnetic insulator : topological insulator (CrBr₃/Bi₂Se₃) heterostructure

Abstract

A heterostructure with the ferromagnetic insulator (FI) and topological insulator (TI) is promising to break the time-reversal symmetry (TRS) of TI by the magnetic proximity effect. The exotic quantum phenomena are possible to be observed. In this thesis, the transport properties of FI/TI heterostructures CrBr₃/Bi₂Se₃ are investigated. In contrast, the transport properties of the control sample Bi₂Se₃ are measured. The anomalous Hall effect (AHE) and the suppression of weak antilocalization effect are observed in the heterostructure suggesting the TRS is broken in the heterostructure system. On the other hand, the AHE cannot be observed in the control sample Bi₂Se₃ and the heterostructure with the large thickness of Bi₂Se₃. The results suggest that two requirements should be fulfilled in order to realize the anomalous Hall effect. First, the CrBr₃ layer should be present to induce magnetism on TI. Second, the thickness of TI should be below 20 nm to reduce the bulk contribution.

Date of Award	2021
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology
Supervisor	Jiannong WANG (Supervisor)