Termination Switching of Antiferromagnetic Proximity Effect in Topological Insulator

Published

August 12, 2020

Author(s)

Chao-Yao Yang, Lei Pan, Alexander Grutter, Haiying Wang, Xiaoyu Che, Qing L. He, Yingying Wu, Dustin A. Gilbert, Padraic Shafer, Elke Arenholz, Hao Wu, Gen Yin, Peng Deng, Julie Borchers, William D. Ratcliff, Kang L. Wang

Abstract

The magnetic proximity effect (MPE) allows exchange-coupling of topological insulators (TIs) with magnetically ordered materials to break time-reversal-symmetry and open a gap in the Dirac-cone surface state, with the goal of realizing quantum anomalous Hall transport without magnetic dopant-induced disorder. In this work, ferromagnetism with a Curie temperature of approximately 120 K has been demonstrated in a heterostructure of TI (Bi,Sb)₂Te₃ (BST) sandwiched between two antiferromagnetic (AFM) CrSe layers. The MPE was shown to be highly-dependent on the stacking order of the heterostructure: growing CrSe on top of BST results in induced ferromagnetism, while growing BST on CrSe yielded no evidence of a MPE. Magnetic X-ray spectroscopy, polarized neutron reflectometry (PNR) and first-principle calculations suggest the MPE is dependent on the CrSe surface termination, which in turn depends strongly on interface symmetry. For the top interface, Cr-termination leads to double-exchange interactions between Cr³⁺ surface states and Cr²⁺ bulk states. This Cr³⁺-Cr²⁺ exchange stabilizes the ferromagnetic order localized at the interface and magnetically polarizes the BST Sb band. In contrast, Se-termination at the CrSe/BST interface yields no detectable MPE. These results directly confirm an antiferromagnetically oriented MPE in TI films and provides a critical insight into the sensitivity of the surface state.

Citation

Science Advances

Volume

6

Issue

33

Pub Type

Journals

Keywords

Quantum materials, topological insulator, proximity effect, antiferromagnet, interface, magnetism, thin film

Citation

Yang, C. , Pan, L. , Grutter, A. , Wang, H. , Che, X. , He, Q. , Wu, Y. , Gilbert, D. , Shafer, P. , Arenholz, E. , Wu, H. , Yin, G. , Deng, P. , Borchers, J. , Ratcliff, W. and Wang, K. (2020), Termination Switching of Antiferromagnetic Proximity Effect in Topological Insulator, Science Advances (Accessed April 19, 2024)