Quantum anomalous Hall effect in intrinsic magnetic topological insulator MnBi ₂ Te ₄

Abstract

In a magnetic topological insulator, nontrivial band topology combines with magnetic order to produce exotic states of matter, such as quantum anomalous Hall (QAH) insulators and axion insulators. In this work, we probe quantum transport in MnBi2Te4 thin flakes—a topological insulator with intrinsic magnetic order. In this layered van der Waals crystal, the ferromagnetic layers couple antiparallel to each other; atomically thin MnBi2Te4, however, becomes ferromagnetic when the sample has an odd number of septuple layers. We observe a zero-field QAH effect in a five–septuple-layer specimen at 1.4 kelvin, and an external magnetic field further raises the quantization temperature to 6.5 kelvin by aligning all layers ferromagnetically. The results establish MnBi2Te4 as an ideal arena for further exploring various topological phenomena with a spontaneously broken time-reversal symmetry.

Predicting large-Chern-number phases in a shaken optical dice lattice

“…However, owing to the limitations of lattice structure, observing large-Chern-number phases in reality remains impossible. Even in topological nontrivial materials, the Chern numbers are mostly detected for C = ±1 [29][30][31]. Rarely, in the context of the photonic crystals [32], Chern numbers are measured up to C = 4 by introducing an external magnetic field.…”

Intrinsic quantum anomalous Hall phase induced by proximity in the van der Waals heterostructure germanene/ Cr2Ge2Te6

“…The compound MnBi 2 Te 4 is stacked in a configuration of Te-Bi-Te-Mn-Te-Bi-Te septuple layers. Significantly, the evidence of zero-field QAH effects has been observed in a fiveseptuple-layer of MnBi 2 Te 4 up to 1.4 K by Deng et.al [23]. Beyond MnBi 2 Te 4 , other vdW superlattice-like Mn-Bi-Te structures with tunable chemical formulas as (MnBi 2 Te 4 ) m (Bi 2 Te 3 ) n (where m and n are integer) have also been proposed [18,[24][25][26].…”

“…Very recently, breakthroughs of intrinsic QAH effects have been achieved in a van der Waals (vdW) layered magnetic TI MnBi 2 Te 4 [18][19][20][21][22][23]. The compound MnBi 2 Te 4 is stacked in a configuration of Te-Bi-Te-Mn-Te-Bi-Te septuple layers.…”

“…Beyond MnBi 2 Te 4 , other vdW superlattice-like Mn-Bi-Te structures with tunable chemical formulas as (MnBi 2 Te 4 ) m (Bi 2 Te 3 ) n (where m and n are integer) have also been proposed [18,[24][25][26]. Through tuning numbers of layers, stacking configurations, or compositions, these vdW heterostructures have been further proposed to investigate rich topological quantum phenomena between magnetism and topology, such as QAH phases [18,20,23], axion insulator states [22], antiferromagnetic TIs [21,22], and their phase transitions [18]. These advances mentioned above forward a strategy for investigating magnetic topological phases and especially QAH effects in vdW layered materials.…”

XFe4Ge2(X=Y,Lu) and Wang1, Tang2, Po3 et al. 2020Phys. Rev. B280420View full textAdd to dashboardCite

“…Compared to the time-reversal-invariant topological materials, magnetic topological materials are also expected to show rich exotic phenomena [35], such as axion insulators [36][37][38][39][40][41][42][43], antiferromagnetic topological insulator [40][41][42][43][44][45][46][47], magnetic Dirac semimetal [48][49][50], and magnetic Weyl semimetals [11,51]. However, the predictions on magnetic TMs are relatively rare and very few of them have been realized in experiments up to now [35].…”