Manganese bismuth telluride

MnBi₂Te₄

Also called MBT, MnSb₂Te₄, MnBi₄Te₇

van der Waals crystal magnet

The first crystal that is both magnetic and topological by itself. In a topological insulator, electricity flows along the surfaces while the inside insulates; add magnetism, and current can be confined to the edges of a thin flake, flowing without loss and without an applied magnetic field. That quantum anomalous Hall effect previously required carefully doped films. In MnBi₂Te₄ every septuple layer carries its own layer of manganese magnetism, and a flake five layers thick showed the effect in 2020.

Cell: Hexagonal, a = 4.33 Å
Atoms per cell: 7
Mn–Te bond: 2.97 Å
Bi–Te bonds: 3.03 and 3.30 Å
Height: 10.91 Å between the outer atom centres

Seven atomic planes, Te–Bi–Te–Mn–Te–Bi–Te: a manganese telluride layer inserted into the middle of a Bi₂Te₃ quintuple layer. Manganese sits in an octahedron of tellurium and carries the magnetic moment. Within one septuple layer the moments align; neighbouring septuple layers point opposite ways, which is why flakes with an odd number of layers are magnetic overall and those with an even number are not. One septuple layer of bulk MnBi₂Te₄ (Lee and colleagues, CrystEngComm 15, 5532, 2013; COD 7210230): a = 4.33 Å, the outer tellurium planes 5.45 Å above and below the manganese.

Data sheet

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Kind of sheet: van der Waals crystal
Peels off a layered crystal, one sheet at a time
Behaves as: magnet
Band gap: Narrow-gap topological insulator with a bulk gap of roughly 0.2 eV; whether its surface state has a magnetic gap is disputed

In colour: this family, 0.2 eV. In grey: the other 39 families on the catalogue’s chart, each at the middle of its range.
Thickness: ~1.4 nm per septuple layer
Structure: Septuple layers, Te–Bi–Te–Mn–Te–Bi–Te, stacked by van der Waals forces (rhombohedral); MnBi₄Te₇ and MnBi₆Te₁₀ insert one or two non-magnetic Bi₂Te₃ quintuple layers between them
Space group: MnBi₂Te₄: bulk R3m, monolayer P3m1
Bulk: the Materials Project crystal linked below. Monolayer: the 2DMatPedia layer, as a periodic slab
Stability: Air-sensitive: surfaces oxidise and hydrolyse quickly, so exfoliation and device fabrication are done under argon, and even brief exposure to air changes transport results.
First made: Predicted and observed as an antiferromagnetic topological insulator in 2019 (Otrokov and colleagues; Gong and colleagues); quantum anomalous Hall effect in a five-layer flake in 2020 (Deng and colleagues)
Materials Project: MnBi₂Te₄
Computed crystal structure and properties
2DMatPedia: MnBi₂Te₄
Computed monolayer, exfoliated from a bulk crystal of the same compound

Compare with other materials

Key properties

A-type antiferromagnet: ferromagnetic within each septuple layer and opposite between neighbouring layers, with TN ≈ 24 K
Quantum anomalous Hall effect at zero field in a five-layer flake at 1.4 K, rising to 6.5 K when a field aligns all the layers
Theory predicts Chern-insulator behaviour for odd and axion-insulator behaviour for even numbers of layers; results in few-layer flakes are sensitive to how devices are made
Reported surface gaps range from about 60 meV to none at all, a disagreement linked to surface magnetism and defects
Antisite defects between Mn and Bi or Sb change the magnetism strongly; in MnSb₂Te₄ they can make the coupling between layers ferromagnetic

How it is made

Bulk crystals by flux growth or chemical vapour transport, within the narrow temperature window where the compound is stable
Mechanical exfoliation and device fabrication entirely inside an argon glovebox
Molecular beam epitaxy of thin films

Uses, and how close they are

Lossless edge-channel electronics and field-free resistance standards based on the quantum anomalous Hall effectlab
A platform for axion electrodynamics and topological magnetoelectric effectslab

Readiness runs lab → prototype → pilot → deployed.

Open problems

Is there a magnetic gap in the surface Dirac cone, and why do different measurements disagree?
Why is the quantum anomalous Hall effect so hard to reproduce between flakes, and can it survive to higher temperatures?
Can defect control or MnBi₄Te₇-type intergrowths give a robust ferromagnetic topological insulator?

Going deeper

Short notes for specialists. Choose a lens in the header and yours comes first.

For theoreticians · your lens

DFT with a Hubbard U on Mn predicts an A-type antiferromagnetic topological insulator with a Z₂ axion index and a gapped surface state; the gapless or weakly gapped surfaces seen in experiments point to surface magnetic reconstruction, disorder or antisite defects. Thin films need layer-resolved Chern-number calculations, with the parity of the layer number deciding between Chern and axion behaviour.

For experimentalists · your lens

Handle everything under argon, and report exact layer numbers from optical contrast and AFM, because parity decides the topology. Transport varies with fabrication, so quantisation claims need several devices and careful control of contacts and gating. ARPES surface gaps depend on the cleave and on the temperature relative to TN.

For engineers · your lens

The quantum anomalous Hall effect it hosts would give lossless edge currents and a resistance standard that needs no magnet, but quantisation still requires a few kelvin and flakes are hard to reproduce. Magnetically doped topological-insulator films remain the more developed route.

In the research tracks

Theory frontiers

Growth methods

MBE and van der Waals epitaxy

Recent news

The newest items tagged MnBi₂Te₄, from the news feed updated 5 Oct 2026.

Preprintnot yet peer reviewed 28 Sep 2026 arXiv

Directional strain control of magnetism in MnBi₂Se₄, MnSb₂Se₄, and MnSb₂Te₄ freestanding monolayers

MnBi₂Se₄, MnSb₂Se₄, and MnSb₂Te4 are layered magnetic quantum materials of interest for spintronic and topological electronic applications, where control of magnetic order at the atomic scale is essential. These materials are particularly sensitive to strain. We investigate their strain-dependent magnetism in the…

TheoryMnBi₂Te₄

Preprintnot yet peer reviewed 22 Sep 2026 arXiv

Spectroscopic signatures of persistent exciton condensation in a bulk magnetic topological insulator

Exciton condensates are long-sought correlated quantum states arising from macroscopic coherence of bound electron-hole pairs. Although equilibrium and transient excitonic states have been reported in several material platforms, direct evidence for a light-induced exciton condensate state has been challenging to…

ExperimentTheoryMnBi₂Te₄

Preprintnot yet peer reviewed 7 Sep 2026 arXiv

Restoring the Surface Magnetic Gap in MnBi₂Te₄

A widespread experimental realization of quantized anomalous transport in the intrinsic magnetic topological insulator MnBi₂Te₄ is hindered by its elusive surface magnetic gap. Uncovering the origin of the gapless states is essential for accessing its topological properties. Here we show that surface defects lower the…

TheoryExperimentMnBi₂Te₄

Preprintnot yet peer reviewed 20 Aug 2026 arXiv

Signatures of a light-induced exciton condensate exhibiting BEC-BCS crossover

Exciton condensates provide a platform to study quasiparticle pairing, Bose-Einstein condensation-Bardeen-Cooper-Schrieffer (BEC-BCS) crossover, and excitonic topological phenomena. Achieving a nonequilibrium exciton condensate allows the ultimate tunability of these emergent phenomena. Yet, evidence of a…

ExperimentTheoryMnBi₂Te₄

Preprintnot yet peer reviewed 2 Aug 2026 arXiv

All-Electric Topological Phase Transitions in Proximity-Coupled Bilayer MnBi2Te4 Heterostructures

The intrinsic magnetic topological insulator MnBi2Te4, in the two-dimensional limit, hosts thickness dependent axion and quantum anomalous Hal (QAH) insulating states governed by antiferromagnetic interlayer coupling. However, controlled interconversion between these phases typically requires extreme external magnetic…