A van der Waals antiferromagnetic topological insulator with weak interlayer magnetic coupling

TL;DR

This paper reports the discovery and characterization of MnBi4Te7, a van der Waals antiferromagnetic topological insulator with weak interlayer magnetic coupling, exhibiting unique surface states and potential for heterostructure engineering.

Contribution

The study introduces MnBi4Te7 as a new van der Waals antiferromagnetic topological insulator with distinct surface states and weak interlayer magnetic coupling, expanding the material platform for quantum phenomena exploration.

Findings

MnBi4Te7 is ferromagnetic in-plane and antiferromagnetic along the c axis.

It exhibits Z2 antiferromagnetic topological insulator properties.

The material's superlattice structure enables potential heterostructure fabrication.

Abstract

Magnetic topological insulators (TI) provide an important material platform to explore quantum phenomena such as quantized anomalous Hall (QAH) effect and Majorana modes, etc. Their successful material realization is thus essential for our fundamental understanding and potential technical revolutions. By realizing a bulk van der Waals material MnBi4Te7 with alternating septuple [MnBi2Te4] and quintuple [Bi2Te3] layers, we show that it is ferromagnetic in plane but antiferromagnetic along the c axis with an out-of-plane saturation field of ~ 0.22 T at 2 K. Our angle-resolved photoemission spectroscopy measurements and first-principles calculations further demonstrate that MnBi4Te7 is a Z2 antiferromagnetic TI with two types of surface states associated with the [MnBi2Te4] or [Bi2Te3] termination, respectively. Additionally, its superlattice nature may make various heterostructures of [MnBi2Te4] and [Bi2Te3] layers possible by exfoliation. Therefore, the low saturation field and the superlattice nature of MnBi4Te7 make it an ideal system to investigate rich emergent phenomena.