Layer Hall effect in a 2D topological axion antiferromagnet

Area of Science:

• Condensed Matter Physics
• Quantum Materials
• Spintronics

Background:

• Antiferromagnets, unlike ferromagnets, lack global magnetization but possess complex microscopic spin structures.
• Topological antiferromagnets exhibit unique properties related to the Berry phase, including distinct spatial textures.
• MnBi2Te4 is an even-layered, two-dimensional antiferromagnetic axion insulator with potential for layer-dependent phenomena.

Purpose of the Study:

• To investigate the Berry phase textures in topological antiferromagnets, specifically in MnBi2Te4.
• To explore the emergence and characteristics of a layer Hall effect in this material.
• To understand the role of the axion field in manipulating the layer-locked Berry curvature.

Main Methods:

• Experimental investigation of the Hall effect in even-layered MnBi2Te4.
• Application of electric fields to induce and measure the layer Hall effect.
• Analysis of the layer-locked Berry curvature and its dependence on the axion field.

Main Results:

• Observation of a significant layer Hall effect in MnBi2Te4, with opposite deflection of electrons between top and bottom layers.
• Absence of anomalous Hall effect under zero electric field, but emergence of a large, layer-polarized effect upon electric field application (approx. 0.5e^2/h).
• Identification of an unusual layer-locked Berry curvature characterizing the axion insulator state, which can be manipulated by the axion field.

Conclusions:

• The layer Hall effect provides a novel method to probe the internal spatial structure of topological antiferromagnets.
• The layer-locked Berry curvature is a key feature of the axion insulator state in MnBi2Te4.
• This work opens avenues for spatial engineering of quantum phenomena in antiferromagnetic materials through layer-specific control.