Layer Hall effect in a 2D topological Axion antiferromagnet

Abstract

While ferromagnets have been known and exploited for millennia, antiferromagnets (AFMs) were only discovered in the 1930s. The elusive nature indicates AFMs' unique properties: At large scale, due to the absence of global magnetization, AFMs may appear to behave like any non-magnetic material; However, such a seemingly mundane macroscopic magnetic property is highly nontrivial at microscopic level, where opposite spin alignment within the AFM unit cell forms a rich internal structure. In topological AFMs, such an internal structure leads to a new possibility, where topology and Berry phase can acquire distinct spatial textures. Here, we study this exciting possibility in an AFM Axion insulator, even-layered MnBi${}_2$Te${}_4$ flakes, where spatial degrees of freedom correspond to different layers. Remarkably, we report the observation of a new type of Hall effect, the layer Hall effect, where electrons from the top and bottom layers spontaneously deflect in opposite directions. Specifically, under no net electric field, even-layered MnBi${}_2$Te${}_4$ shows no anomalous Hall effect (AHE); However, applying an electric field isolates the response from one layer and leads to the surprising emergence of a large layer-polarized AHE (~50%$\frac{e^2}{h}$). Such a layer Hall effect uncovers a highly rare layer-locked Berry curvature, which serves as a unique character of the space-time $\mathcal{P}\mathcal{T}$-symmetric AFM topological insulator state. Moreover, we found that the layer-locked Berry curvature can be manipulated by the Axion field, E$\cdot$B, which drives the system between the opposite AFM states. Our results achieve previously unavailable pathways to detect and manipulate the rich internal spatial structure of fully-compensated topological AFMs. The layer-locked Berry curvature represents a first step towards spatial engineering of Berry phase, such as through layer-specific moiré potential.

A revised version of this article is published in Nature

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Cited by in corpus (12)

• Quantum metric nonlinear Hall effect in a topological antiferromagnetic heterostructure
• Switchable anomalous Hall effects in polar-stacked 2D antiferromagnet MnBi2Te4
• Half-Quantized Hall Effect and Power Law Decay of Edge Current Distribution
• AC susceptometry of 2D van der Waals magnets enabled by the coherent control of quantum sensors
• Crystal structure and Raman active lattice vibrations of magnetic topological insulators MnBi2Te4 n(Bi2Te3) (n = 0, 1, . . . , 6)
• Nonreciprocal transport in a bilayer of MnBi2Te4 and Pt
• Valley contrasting bulk photovoltaic effect in antiferromagnetic MnPSe${}_3$ monolayer
• Influences of the dissipative topological edge state on quantized transport in MnBi2Te4
• Layer Control of Magneto-Optical Effects and Their Quantization in Spin-Valley Splitting Antiferromagnets
• Effective action approach to the filling anomaly in crystalline topological matter
• Antiferromagnetic topological insulating state in Tb${}_{0.02}$Bi${}_{1.08}$Sb${}_{0.9}$Te${}_2$S single crystals
• Magneto-optical Kerr and Faraday effects in bilayer antiferromagnetic insulators