Antiferromagnetic Topological Insulator with Nonsymmorphic Protection in Two Dimensions

Niu, Chengwang; Wang, Hao; Mao, Ning; Huang, Baibiao; Mokrousov, Yuriy; Dai, Ying

doi:10.1103/physrevlett.124.066401

Cited by 77 publications

(53 citation statements)

References 64 publications

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“…CeAlGe is also considered to be a magnetic type-II Weyl semimetal without AHE due to an antiferromagnetic (AFM) ground state [18]. Recent studies show that AFM topological states provide an exciting platform for exploring prominent physics and applications of AFM spintronics [19,20].…”

Section: Introductionmentioning

confidence: 99%

Field-induced tricritical phenomenon and magnetic structures in magnetic Weyl semimetal candidate NdAlGe

et al. 2022

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Non-centrosymmetric NdAlGe is considered to be a candidate for magnetic Weyl semimetal in which the Weyl nodes can be moved by magnetization. Clarification of the magnetic structures and couplings in this system is thus crucial to understand its magnetic topological properties. In this work, we conduct a systematical study of magnetic properties and critical behaviors of single-crystal NdAlGe. Angle-dependent magnetization exhibits strong magnetic anisotropy along the c-axis and absolute isotropy in the ab-plane. The study of critical behavior with H//c gives critical exponents β = 0.236(2), γ = 0.920(1), and δ = 4.966(1) at critical temperature TC = 5.2(2) K. Under the framework of the universality principle, M(T, H) curves are scaled into universality curves using these critical exponents, demonstrating reliability and self-consistency of the obtained exponents. The critical exponents of NdAlGe are close to the theoretical prediction of a tricritical mean-field model, indicating a field-induced tricritical behavior. Based on the scaling analysis, a H −T phase diagram for NdAlGe with H//c is constructed, revealing a ground state with an up-up- down spin configuration. The phase diagram unveils multiple phases including up-up-down domains, up-up-down ordering state, polarized ferromagnetic (PFM), and paramagnetic (PM) phases, with a tricritical point (TCP) located at the intersection [TT CP = 5.27(1) K, HT CP = 30.1(3) kOe] of up-up-down, PFM, and PM phases. The multiple phases and magnetic structures imply a delicate competition and balance between variable interactions and couplings, laying a solid foundation for unveiling topological properties and critical phenomena in this system.

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Section: Introductionmentioning

confidence: 99%

Field-induced tricritical phenomenon and magnetic structures in magnetic Weyl semimetal candidate NdAlGe

et al. 2022

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“…The 2D Janus TMD MSSe (M = Mo and W) monolayers have been predicted as ferroelastic TI 3 , and the In 2 Te 3 /In 2 Se 3 bilayer heterostructure as ferroelectric TI 4 . Antiferromagnetic TI with coexistence of intrinsic antiferromagnetism and QSH states also has been reported in XMnY (X=Sr and Ba; Y=Sn and Pb) quintuple layers 5 , as promising candidates for innovative spintronics applications. Piezoelectricity and band topology are two extensively studied distinct properties of insulators, and their coexistence in a single 2D material may lead to novel physical phenomenon and device applications.…”

Section: Introductionmentioning

confidence: 82%

Piezoelectric quantum spin Hall insulator with Rashba spin splitting in Janus monolayer $\mathrm{SrAlGaSe_4}$

Guo,

Zhu,

et al. 2021

Preprint

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The realization of multifunctional two-dimensional (2D) materials is fundamentally intriguing, such as combination of piezoelectricity with topological insulating phase or ferromagnetism. In this work, a Janus monolayer SrAlGaSe4 is built from 2D MA2Z4 family with dynamic, mechanical and thermal stabilities, which is piezoelectric due to lacking inversion symmetry. The unstrained SrAlGaSe4 monolayer is a narrow gap normal insulator (NI) with spin orbital coupling (SOC). However, the NI to topological insulator (TI) phase transition can be induced by the biaxial strain, and a piezoelectric quantum spin Hall insulator (PQSHI) can be achieved. More excitingly, the phase transformation point is only about 1.01 tensile strain, and nontrivial band topology can hold until considered 1.16 tensile strain. Moreover, a Rashba spin splitting in the conduction bands can exit in PQSHI due to the absence of a horizontal mirror symmetry and the presence of SOC. For monolayer SrAlGaSe4, both in-plane and much weak out-of-plane piezoelectric polarizations can be induced with a uniaxial strain applied. The calculated piezoelectric strain coefficients d11 and d31 of monolayer SrAlGaSe4 are -1.865 pm/V and -0.068 pm/V at 1.06 tensile strain as a representative TI. In fact, many PQSHIs can be realized from 2D MA2Z4 family. To confirm that, similar to SrAlGaSe4, the coexistence of piezoelectricity and topological orders can be realized by strain (about 1.04 tensile strain) in the CaAlGaSe4 monolayer. Our works suggest that Janus monolayer SrAlGaSe4 is a pure 2D system for PQSHI, enabling future studies exploring the interplay between piezoelectricity and topological orders, which can lead to novel applications in electronics and spintronics.

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“…We perform a model calculation to show that 6-SL MnBi 2 Te 4 at zero field is actually an AFM QSH state hosting helical edge states. The intrinsic magnetic TI MnBi 2 Te 4 can be described by a 3D version of 3D AFM TI 35,36 . Such AFM QSH is usually protected by a combined symmetry of TRS and one other spatial symmetry, which makes it different from non-magnetic QSH protected only by TRS [37][38][39] .…”

Section: Discussionmentioning

confidence: 99%

Direct visualization of edge state in even-layer MnBi2Te4 at zero magnetic field

Lin

Feng

Wang

et al. 2021

Preprint

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Being the first intrinsic antiferromagnetic (AFM) topological insulator, MnBi2Te4 is argued to be a topological axion state in its even-layer form due to the antiparallel magnetization between the top and bottom layers. Here we combine both transport and scanning microwave impedance microscopy (sMIM) to investigate such axion state in atomically thin MnBi2Te4 with even-layer thickness at zero magnetic field. While transport measurements show a zero Hall plateau signaturing the axion state, sMIM uncovers an unexpected edge state raising questions regarding the nature of the “axion state”. Based on our model calculation, we propose that the even-layer MnBi2Te4 at zero field is in an AFM quantum spin Hall (QSH) state hosting a pair of helical edge states. Such novel AFM QSH is originated from the combination of half translation symmetry and time-reversal symmetry in MnBi2Te4. Our finding thus signifies the richness of topological phases in MnB2Te4 that has yet to be fully explored.

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Antiferromagnetic Topological Insulator with Nonsymmorphic Protection in Two Dimensions

Cited by 77 publications

References 64 publications

Field-induced tricritical phenomenon and magnetic structures in magnetic Weyl semimetal candidate NdAlGe

Field-induced tricritical phenomenon and magnetic structures in magnetic Weyl semimetal candidate NdAlGe

Piezoelectric quantum spin Hall insulator with Rashba spin splitting in Janus monolayer $\mathrm{SrAlGaSe_4}$

Direct visualization of edge state in even-layer MnBi2Te4 at zero magnetic field

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