Metamagnetic quantum criticality in the antiferromagnetic topological insulator MnBi${}_2$Te${}_4$

Abstract

Combining transport and magnetization measurements, we discover the emergence of a tricritical point connecting the antiferromagnetic, metamagnetic and paramagnetic regions in MnBi${}_2$Te${}_4$, a magnetic topological insulator candidate which can potentially exhibit axion electrodynamics. We observe a unique magnetic field-driven phase diagram where the second-order antiferromagnetic to paramagnetic phase boundary bifurcates into two first-order lines at the tricritical point. The two first-order lines enclosing the metamagnetic phase eventually terminate at the quantum critical endpoints with the application of magnetic field.