Quantum anomalous hall effect in collinear antiferromagnetism

Abstract

The two-dimensional Quantum Hall effect with no external magnetic field is called the Quantum anomalous Hall (QAH) effect. So far, experimentally realized QAH insulators all exhibit ferromagnetic order and the QAH effect only occurs at very low temperatures. On the other hand, up to now the QAH effect in collinear antiferromagnetic (AFM) materials has never been reported and the corresponding mechanism has never been proposed. In this work, we realize the QAH effect by proposing a four-band lattice model with static AFM order, which indicates that the QAH effect can be found in AFM materials. Then, as a prototype, we demonstrate that a monolayer CrO can be switched from an AFM Weyl semimetal to an AFM QAH insulator by applying strain, based on symmetry analysis and the first-principles electronic structure calculations. Our work not only proposes a scenario to search for QAH insulators in materials, but also reveals a way to considerably increase the critical temperature of the QAH phase.

How to produce spin-splitting in antiferromagnetic materials

“…The altermagnetism is characterized by crystal-rotation symmetries connecting opposite-spin sublattices separated in the real space, which leads to opposite-spin electronic states separated in the momentum space. Several bulk materials and two-dimensional (2D) materials have been predicted to be altermagnetism, such as RuO 2 [19], FeF 2 [20], MnTe [21], some organic AFMs [22], MnF 2 [23], some GdFeO 3 -type perovskites [24], Cr 2 O 2 [25,26], Cr 2 SO [27] and V 2 Se 2 O [28]. Spontaneous antisymmetric spin splitting has also been reported in noncollinear antiferromagnets without SOC [29].…”

Magnetization direction-controlled topological band structure in TlTiX (X = Si, Ge) monolayers

“…Hence, achieving the QAH effect has become an exceedingly significant focal point within the realm of condensed matter physics. To date, several realistic QAH insulators have been successively predicted by theoretical calculations and confirmed by multiple experimental techniques such as angleresolved photoemission spectroscopy and electrical transport measurements [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. The first observation of the QAH effect occurred in thin films of (Bi; Sb) 2 Te 3 doped with Cr at extremely low temperatures (below 30 mK) due to the weak magnetic coupling in the doped Cr atoms and the narrow band gap of the material [25].…”

Insight into the quantum anomalous Hall states in two-dimensional kagome Cr3Se4 and Fe3S4 monolayers

“…In the past few decades, quantum anomalous Hall (QAH) insulators (Chern insulators), with spin-momentum locked dissipationless gapless edge states inside the bulk energy gaps, have attracted tremendous attention in condensed matter physics. [1][2][3][4][5][6][7][8] The QAH effect generally requires two fundamental factors: the ferromagnetic (FM) ground state and spin-orbit coupling (SOC). [9][10][11][12][13][14][15][16] The transport feature of QAH insulators is not affected by perturbations and disorders, and the chiral edge state can be used as a dissipative transmission channel to transmit and store information.…”