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
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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
摘要：
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QuantumanomalousHalleffectscontrolledbychiraldomainwallsQiruiCui1,JinghuaLiang1,YingmeiZhu1,XiongYao1,HongxinYang1,2*1NingboInstituteofMaterialsTechnologyandEngineering,ChineseAcademyofSciences,Ningbo315201,China2CenterofMaterialsScienceandOptoelectronicsEngineering,UniversityofChineseAcademyofScien...
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分类：图书资源
价格：10玖币
属性：19 页
大小：1.45MB
格式：PDF
时间：2025-04-24
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