Quantum anomalous Hall effects controlled by chiral domain walls Qirui Cui1 Jinghua Liang1 Yingmei Zhu1 Xiong Yao1 Hongxin Yang1 2 1Ningbo Institute of Materials Technology and Engineering Chinese Academy of Sciences Ningbo

2025-04-24 1 0 1.45MB 19 页 10玖币

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Quantum anomalous Hall effects controlled by chiral domain walls

Qirui Cui1, Jinghua Liang1, Yingmei Zhu1, Xiong Yao1, Hongxin Yang1, 2*

1Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo

315201, China

2Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of

Sciences, Beijing 100049, China

*Corresponding author: hongxin.yang@nimte.ac.cn

Abstract

We report the interplay between two different topological phases in condensed matter physics, the

magnetic chiral domain wall (DW) and the quantum anomalous Hall (QAH) effect. We show that

the chiral DW driven by Dzyaloshinskii–Moriya interaction (DMI) can divide the uniform domain

into several zones where the neighboring zone possesses opposite quantized Hall conductance. The

separated domain with a chiral edge state (CES) can be continuously modified by external magnetic

field-induced domain expansion and thermal fluctuation, which gives rise to the reconfigurable

QAH effect. More interestingly, we show that the position of CES can be tuned by spin current

driven chiral DW motion. Several two-dimensional magnets with high Curie temperature and large

topological band gaps are proposed for realizing these phenomena. Our work thus reveals the

possibility of chiral DW controllable QAH effects.

The magnetic chiral DW is a type of topological defect with discrete symmetry, which is the

boundary between domains with opposite magnetization and could be excited from uniform domain

ground states. The topological charge of chiral DW is defined as: QDW = (1/)



 , where

 represents the polar angle of normalized spin vector S. QDW equals 1 or -1 when S rotates from

+z to -z or -z to +z. Domains separated by the chiral DW with topological protection is widely used

as the information bit in emergent spintronic memory and logic devices, and the current-driven chiral

DW displacement via spin-transfer torque (STT) or SOT underpins the operations of these devices

[1-9]. Notably, one key term for stabilizing the chiral DW is DMI which favors the formation of

noncollinear spin configuration in magnets lacking inversion symmetry [10-14].

QAH effect is another type of topological phases, which is characterized by the quantized Hall

conductance (Ce2)/h without external magnetic field (where C, e, and h represents Chern number,

elementary charge, and Planck constant respectively). Due to its dissipationless CESs, QAH effect

shows promising for applications in future electronic devices with ultralow-energy consumption

[15-20] and provides an intriguing platform to investigate topological quantum physics, such as

chiral topological superconductivity and Majorana fermions [21-25]. QAH effect is initially

predicted by Haldane in 1988 [26] and first observed in magnetically doped topological insulator,

Cr-doped (Bi, Sb)2Te3 thin films, by Xue et al in 2013 [17]. However, the extremely low full

quantization temperature of 30 mK largely impedes its practical applications. Thus, tremendous

efforts have been devoted to optimizing and designing material systems with high QAH effect

temperature [27-33]. Besides high temperature, it is a long-sought goal for QAH effect that realizing

effective manipulation of CESs, which probably leads to the artificial designing of quantum

information transferring [34, 35]. In Cr-doped (Bi, Sb)2Te3 thin films, Yasuda et al demonstrate that

two CESs would co-propagate along the DW [36-38] and first realize the reconfigurable CESs by

using the tip of magnetic force microscope to write domain [34]. However, the investigation of

interaction between two topological phases, chiral DW and QAH effect, in realistic materials

remains very limited as far as we know, and particularly, it is still interesting and challenging to

utilize chiral DW to control the high-temperature QAH effects.

As shown in Fig. 1, the coexistence of QAH effect and chiral DW require that materials

combine nontrivial electronic states and sizable DMI. Importantly, the nontrivial topological gap

should appear when magnetization is out-of-plane (OOP) and totally vanish when magnetization is

in-plane (IP), thus resulting in chiral DW being an intrinsic boundary separating two parallel chiral

states. Since CESs are intimately hinged with spin configurations, the approaches that are applied

for controlling spin configurations will eventually lead to the CESs modification. For example, the

spin vector can be aligned by a uniform magnetic field; spin fluctuations can be induced by laser or

thermal excitations; and spin vector orientation can be explicitly and energy-efficiently controlled

by spin current-generated torque. In the following, based on the first-principles calculations,

Wannier-based tight binding models, and atomic spin model simulations, we first take VSe2

monolayer with 4

2 layer group as a representative example to demonstrate the manipulation of

QAH effect via chiral DW, and then extend the discussions to other thin films, i.e., Fe2XI (X=Cl, Br)

Janus monolayers with 4 layer group. The computational methods are given in the

supplemental materials (SM) [39].

The crystal structure of VSe2 is shown in the Fig. S1(a)-(c). Each V atom is tetrahedrally

surrounded by four Se atoms, and a Se atom bonding with two V atoms along x and y directions

locates at bottom and top layer respectively. The calculations of phonon spectrum [Fig. S2(a)]

demonstrates the dynamic stability. To investigate magnetic properties, we adopt the following spin

Hamiltonian:

=, 

,()

, × 

, (1)

where J1 and J2 represent the NN and NNN exchange coupling, respectively, A refers to the single-

ion magnetic anisotropy, and  refers to the DMI between NN V pairs. For extracting magnetic

parameters in spin Hamiltonian, we apply the energy mapping methods [detailed discussion given

in SM], and the results are shown in Table SI. J1 in pristine VSe2 reaches to 39.44 meV implying

strong ferromagnetic exchange coupling between V atoms. Despite J2 = -1.12 meV favoring

antiferromagnetic coupling, its magnitude is much smaller compared with J1. VSe2 possesses

perpendicular magnetic anisotropy of 0.47 meV which is an essential condition for achieving large

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QuantumanomalousHalleffectscontrolledbychiraldomainwallsQiruiCui1,JinghuaLiang1,YingmeiZhu1,XiongYao1,HongxinYang1,2*1NingboInstituteofMaterialsTechnologyandEngineering,ChineseAcademyofSciences,Ningbo315201,China2CenterofMaterialsScienceandOptoelectronicsEngineering,UniversityofChineseAcademyofScien...

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Quantum anomalous Hall effects controlled by chiral domain walls Qirui Cui1 Jinghua Liang1 Yingmei Zhu1 Xiong Yao1 Hongxin Yang1 2 1Ningbo Institute of Materials Technology and Engineering Chinese Academy of Sciences Ningbo.pdf

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Quantum anomalous Hall effects controlled by chiral domain walls Qirui Cui1 Jinghua Liang1 Yingmei Zhu1 Xiong Yao1 Hongxin Yang1 2 1Ningbo Institute of Materials Technology and Engineering Chinese Academy of Sciences Ningbo

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