Evidence for a Magnetic-Field-Induced Ideal Type-II Weyl State in Antiferromagnetic Topological Insulator 
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Lee, Seng Huat; Graf, David; Min, Lujin; Zhu, Yanglin; Yi, Hemian; Ciocys, Samuel; Wang, Yuanxi; Choi, Eun Sang; Basnet, Rabindra; Fereidouni, Arash; Wegner, Aaron; Zhao, Yi-Fan; Verlinde, Katrina; He, Jingyang; Redwing, Ronald; Gopalan, Venkatraman; Churchill, Hugh; Lanzara, Alessandra; Samarth, N.; Chang, Cui-Zu; Hu, Jin; Mao, Zhiqiang

doi:10.1103/physrevx.11.031032

Cited by 44 publications

(51 citation statements)

References 76 publications

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“…For example, in doped magnetic topological insulator quantum well (Mn, Hg) Te 23 , the increase of magnetic field first leads to a transition from C = 2 to C = 1 due to linear Hall effect, then back to C = 2 state attributed to the effective nonlinear Zeeman effect of Mn ions. A recent theoretical study 24 25,26 . So, Landau level could originate either from the surface band in a standard magnetic topological insulator picture 15 , or from the quantum well states in a confined Weyl semimetal picture 18 .…”

Section: Resultsmentioning

confidence: 99%

Electric control of a canted-antiferromagnetic Chern insulator

et al. 2022

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The interplay between band topology and magnetism can give rise to exotic states of matter. For example, magnetically doped topological insulators can realize a Chern insulator that exhibits quantized Hall resistance at zero magnetic field. While prior works have focused on ferromagnetic systems, little is known about band topology and its manipulation in antiferromagnets. Here, we report that MnBi2Te4 is a rare platform for realizing a canted-antiferromagnetic (cAFM) Chern insulator with electrical control. We show that the Chern insulator state with Chern number C = 1 appears as the AFM to canted-AFM phase transition happens. The Chern insulator state is further confirmed by observing the unusual transition of the C = 1 state in the cAFM phase to the C = 2 orbital quantum Hall states in the magnetic field induced ferromagnetic phase. Near the cAFM-AFM phase boundary, we show that the dissipationless chiral edge transport can be toggled on and off by applying an electric field alone. We attribute this switching effect to the electrical field tuning of the exchange gap alignment between the top and bottom surfaces. Our work paves the way for future studies on topological cAFM spintronics and facilitates the development of proof-of-concept Chern insulator devices.

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Section: Resultsmentioning

confidence: 99%

Electric control of a canted-antiferromagnetic Chern insulator

et al. 2022

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“…For instance, the Mn(Bi,Sb) 2n Te 3 n + 1 family of layered antiferromagnets is the first experimental realization of intrinsic magnetic order in topological insulators 7 – 9 . The interlayer magnetic order is intimately connected to the band topology, with experimental demonstration of switching between quantum anomalous Hall and axion insulator states 10 , and realization of a field-driven Weyl semimetal state 11 . In this context, the discovery of new, efficient coupling pathways between the interlayer exchange and other microscopic degrees of freedom would not only add to the rich spectrum of low-dimensional magnetic phenomena, but also potentially unlock pathways for the dynamic manipulation of magnetism and band topology.…”

Section: Introductionmentioning

confidence: 99%

Interlayer magnetophononic coupling in MnBi2Te4

et al. 2022

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The emergence of magnetism in quantum materials creates a platform to realize spin-based applications in spintronics, magnetic memory, and quantum information science. A key to unlocking new functionalities in these materials is the discovery of tunable coupling between spins and other microscopic degrees of freedom. We present evidence for interlayer magnetophononic coupling in the layered magnetic topological insulator MnBi2Te4. Employing magneto-Raman spectroscopy, we observe anomalies in phonon scattering intensities across magnetic field-driven phase transitions, despite the absence of discernible static structural changes. This behavior is a consequence of a magnetophononic wave-mixing process that allows for the excitation of zone-boundary phonons that are otherwise ‘forbidden’ by momentum conservation. Our microscopic model based on density functional theory calculations reveals that this phenomenon can be attributed to phonons modulating the interlayer exchange coupling. Moreover, signatures of magnetophononic coupling are also observed in the time domain through the ultrafast excitation and detection of coherent phonons across magnetic transitions. In light of the intimate connection between magnetism and topology in MnBi2Te4, the magnetophononic coupling represents an important step towards coherent on-demand manipulation of magnetic topological phases.

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“…Therefore, similarly to MnBi 2 Te 4 , very strong fields of up to 60-70 T are needed to overcome the intrablock AFM coupling and fully polarize the SLs. In the Mn(Bi 1−x Sb x ) 2 Te 4 solid solutions, the M (H) behavior, observed in MnSb 2 Te 4 , continuously evolves into that of MnBi 2 Te 4 15,70 . The latter facts strongly point towards the ferrimagnetic structure of the MnBi 2 Te 4 SLs as well.…”

Section: Discussionmentioning

confidence: 98%

Native point defects and their implications for the Dirac point gap at MnBi$_2$Te$_4$(0001)

Garnica¹,

Otrokov²,

Aguilar³

et al. 2021

Preprint

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The Dirac point gap at the surface of the antiferromagnetic topological insulator MnBi2Te4 is a highly debated issue. While the early photoemission measurements reported on large gaps in agreement with theoretical predictions, other experiments found vanishingly small splitting of the MnBi2Te4 Dirac cone. Here, we study the crystalline and electronic structure of MnBi2Te4(0001) using scanning tunneling microscopy/spectroscopy (STM/S), micro(µ)-laser angle resolved photoemission spectroscopy (ARPES), and density functional theory (DFT) calculations. Our topographic STM images clearly reveal features corresponding to point defects in the surface Te and subsurface Bi layers that we identify with the aid of STM simulations as BiTe antisites (Bi atoms at the Te sites) and MnBi substitutions (Mn atoms at the Bi sites), respectively. X-ray diffraction (XRD) experiments further evidence the presence of cation (Mn-Bi) intermixing. Altogether, this affects the distribution of the Mn atoms, which, inevitably, leads to a deviation of the MnBi2Te4 magnetic structure from that predicted for the ideal crystal structure. Our transport measurements suggest that the degree of this deviation varies from sample to sample. Consistently, the ARPES/STS experiments reveal that the Dirac point gap of the topological surface state is different for different samples/sample cleavages. Our DFT surface electronic structure calculations show that, due to the predominant localization of the topological surface state near the Bi layers, MnBi defects can cause a strong reduction of the MnBi2Te4 Dirac point gap, given the recently proved antiparallel alignment of the MnBi moments with respect to those of the Mn layer. Our results provide a key to puzzle out the MnBi2Te4 Dirac point gap mystery.

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Evidence for a Magnetic-Field-Induced Ideal Type-II Weyl State in Antiferromagnetic Topological Insulator Mn(Bi1−xSbx)

Cited by 44 publications

References 76 publications

Electric control of a canted-antiferromagnetic Chern insulator

Electric control of a canted-antiferromagnetic Chern insulator

Interlayer magnetophononic coupling in MnBi2Te4

Native point defects and their implications for the Dirac point gap at MnBi$_2$Te$_4$(0001)

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