Colloquium: Quantum anomalous Hall effect

Chang, Cui-Zu; Liu, Chaoxing; MacDonald, Allan H.

doi:10.48550/arxiv.2202.13902

Cited by 7 publications

(8 citation statements)

References 307 publications

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“…For example, there have been experimental observations of quantum anomalous Hall (QAH) states in twisted bilayer graphene [2,3] and AB stacked MoTe 2 /WSe 2 heterobilayers [4,5]. Unlike other QAH state platforms, such as magnetic doped topological insulator thin film [6][7][8][9][10][11] and MnBi 2 Te 4 [12] in which the topological states can be understood from singleparticle band structures, the bands in moiré materials are typically very narrow (several to tens of meV) so that Coulomb interactions cannot be neglected. A possible path to obtain QAH states is to first create moiré Chern bands at each valley and lift the valley degeneracy through interactions.…”

Section: Introductionmentioning

confidence: 99%

Topological $p_x+ip_y$ inter-valley coherent state in Moiré MoTe$_2$/WSe$_2$ heterobilayers

Xie¹,

Zhang²,

Law³

2022

Preprint

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Recently, a quantum anomalous Hall (QAH) state was observed in AB stacked moiré MoTe2/WSe2 heterobilayers at half-filling. More recent layer-resolved magnetic circular dichroism (MCD) measurements revealed that spin-polarized moiré bands from both the MoTe2 and the WSe2 layers are involved at the formation of the QAH state. This scenario is not expected by existing theories. In this work, we suggest that the observed QAH state is a new state of matter, namely, a topological px + ipy inter-valley coherent state (TIVC). We point out that the massive Dirac spectrum of the MoTe2 moiré bands, together with the Hund's interaction and the Coulomb interactions give rise to this novel QAH state. Through a self-consistent Hartree-Fock analysis, we find a wide range of interaction strengths and displacement fields that the px + ipy-pairing phase is energetically favourable. Besides explaining several key features of the experiments, our theory predicts that the order parameter would involve the pairing of electrons and holes with a definite momentum mismatch such that the pairing would generate a new unit cell which is three times the size of the original moiré unit cell, due to the order parameter modulations.

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Section: Introductionmentioning

confidence: 99%

Topological $p_x+ip_y$ inter-valley coherent state in Moiré MoTe$_2$/WSe$_2$ heterobilayers

Xie¹,

Zhang²,

Law³

2022

Preprint

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“…The quantum anomalous Hall (QAH) effect represents one of the triumphs in conceptualizing topological aspects of electronic states in condensed matter physics [1][2][3][4][5][6][7][8][9][10]. It constitutes an ever-evolving family of Hall effects [11].…”

Section: Introductionmentioning

confidence: 99%

Progress and prospects in the quantum anomalous Hall effect

Chi¹,

Moodera²

2022

Preprint

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The quantum anomalous Hall effect refers to the quantization of Hall effect in the absence of applied magnetic field. The quantum anomalous Hall effect is of topological nature and well suited for field-free resistance metrology and low-power information processing utilizing dissipationless chiral edge transport. In this Perspective, we provide an overview of the recent achievements as well as the materials challenges and opportunities, pertaining to engineering intrinsic/interfacial magnetic coupling, that are expected to propel future development of the field.

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“…2,3 The backscattering-free spin-polarized current of quantum anomalous Hall insulators and the quantized magnetoelectric effect of axion insulators are expected to pave the way for spintronics and quantum computing. [1][2][3][4][5] Recently, the magnetic proximity effect at the interface between a magnetic material and a topological insulator has attracted a lot of attention along with several controversies as one of the methods to break the time-reversal symmetry of the topological insulator surface. 2,3,[6][7][8][9][10][11][12] Anomalous Hall effect measurements and spin-polarized neutron reflectivity measurements in bilayers of magnetic materials and topological insulators reported proximity-induced ferromagnetic ordering at the topological insulator surface.…”

Section: Introductionmentioning

confidence: 99%

Electron spin resonance study of mixed Bi2Se3 topological insulator-magnetic insulator nanoparticles

Lee¹,

Lee²,

Lee³

2022

Preprint

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We investigated Bi2Se3 topological insulator nanoparticles mixed with room-temperature ferromagnetic insulator nanoparticles by using electron spin resonance (ESR) of the surface conduction electrons in the Bi2Se3 nanoparticles. The ESR intensity and linewidth as a function of the molar ratio of the magnetic insulator show the room temperature magnetic proximity effect due to the short-range exchange field of the magnetic insulator nanoparticles along with the long-range magnetic dipole field effect and the surface-to-volume ratio effect.

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Colloquium: Quantum anomalous Hall effect

Cited by 7 publications

References 307 publications

Topological $p_x+ip_y$ inter-valley coherent state in Moiré MoTe$_2$/WSe$_2$ heterobilayers

Topological $p_x+ip_y$ inter-valley coherent state in Moiré MoTe$_2$/WSe$_2$ heterobilayers

Progress and prospects in the quantum anomalous Hall effect

Electron spin resonance study of mixed Bi2Se3 topological insulator-magnetic insulator nanoparticles

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