Effect of antiferromagnetic order on topological electronic structure in Eu-substituted Bi2Se3 single crystals

Soo-Whan Kim,Jun Sung Kim,Jae-Hoon Park,Ki-Seok Kim,Kyoung-Min Kim,Myung-Hwa Jung,Jinsu Kim,Hoil Kim,Jeong-Kyu Kim,Woo-Suk Noh

doi:10.1063/5.0027947

Abstract

Topological antiferromagnetic spintronics is an emerging field due to advantages such as no stray field effect and high-speed dynamics. In bismuth chalcogenide topological insulators, the coexistence of long-range antiferromagnetic order and topologically protected states has scarcely been observed. Here, an antiferromagnetic order, which sets in the direction of magnetic moments perpendicular to the c axis, is introduced by Eu substitution in Bi2Se3, and therefore it influences the topological electronic properties of Bi2Se3. Despite Eu substitution, Shubnikov–de Haas (SdH) oscillations are observed. The angle dependence of SdH oscillations shows a signature of anisotropic 3D Fermi surfaces with a nontrivial Berry phase by Eu substitution, and the temperature dependence of SdH oscillations reveals that the effective mass is comparable to the pristine Bi2Se3. These results suggest that the nontrivial topological state can survive in the antiferromagnetic order of Eu-substituted Bi2Se3. Our work expands the base of topological materials available for antiferromagnetic spintronics applications.

Highlights

The angle dependence of Shubnikov–de Haas (SdH) oscillations shows a signature of anisotropic 3D Fermi surfaces with a nontrivial Berry phase by Eu substitution, and the temperature dependence of SdH oscillations reveals that the effective mass is comparable to the pristine Bi2Se3
The results reveal that the effective mass of EBS is comparable with that of the pristine Bi2Se3 even though the antiferromagnetic order is introduced after the Eu substitution
The analyses of angle-dependent SdH oscillations show a deviation from 1/cos(θ) scaling and a π Berry phase shift at θ < 45○, which is an indication of the 3D Fermi surface and nontrivial topological states by Eu substitution

Summary

Introduction

Antiferromagnetic topological insulators (AFM TIs) have attracted great interest due to the expectation that these can be used for the application of spintronics, which is an emerging field.1–3 The advantages of AFM materials in spintronics are negligible stray field, lower current density, and faster spin dynamics, compared to ferromagnetic materials.1,2 In addition, AFM materials with topologically protected states have been proposed to achieve properties such as spin-momentum locking, strong magnetoresistance, and high mobility of the relativistic electrons.3 Recent studies have provided some instances of topological AFM spintronics that show large anomalous Hall effect, antiferromagnetic spin resonance, and topological metal–insulator transition.3–6 For nonmagnetic bismuth chalcogenides such as Bi2Se3 and Bi2Te3, proven as TIs, the doping of transition metals or rare-earth metals is the key to realize the bulk magnetic order. An antiferromagnetic order, which sets in the direction of magnetic moments perpendicular to the c axis, is introduced by Eu substitution in Bi2Se3, and it influences the topological electronic properties of Bi2Se3.

Results

Conclusion