Antiferromagnetic $\mathbb{Z}_2$ topological metal near the metal-insulator transition in MnS$_2$

TL;DR

This paper reveals that MnS$_2$ undergoes pressure-induced topological phase transitions, including a $ ext{Z}_2$ topological metal and Weyl metal phases, driven by band inversion and magnetic order, with implications for magnetic topological materials and spintronics.

Contribution

It demonstrates the realization of a $ ext{Z}_2$ topological antiferromagnetic metal in MnS$_2$, confirming a theoretical prediction in a real material.

Findings

Pressure induces a topological band inversion in MnS$_2$.

MnS$_2$ exhibits a $ ext{Z}_2$ topological antiferromagnetic metal phase.

Transition to Weyl metal phase at higher pressures.

Abstract

Antiferromagnetic (AFM) semiconductor MnS$_2$ possesses both high-spin and low-spin magnetic phases that can be reversibly switched by applying pressure. With increasing pressure, the high-spin state undergoes pressure-induced metalization before transforming into a low-spin configuration, which is then closely followed by a volume collapse and structural transition. We show that the pressure driven band inversion is in fact topological, resulting in an antiferromagnetic $\mathbb{Z}_2$ topological metal (Z2AFTM) phase with a small gap and a Weyl metal phase at higher pressures, both of which precede the spin-state crossover and volume collapse. In the Z2AFTM phase, the magnetic order results in a doubling of the periodic unit cell, and the resulting folding of the Brillouin zone leads to a $\mathbb{Z}_2$ topological invariant protected by the persisting combined time-reversal and half-translation symmetries. Such a topological phase was proposed theoretically by Mong, Essin, and Moore in 2010 for a system with AFM order on a face-centered cubic (FCC) lattice, which until now has not been found in the pool of real materials. MnS$_2$ represents a realization of this original proposal through AFM order on the Mn FCC sublattice. A rich phase diagram of topological and magnetic phases tunable by pressure, establishes MnS$_2$ as a candidate material for exploring magnetic topological phase transitions and for potential applications in AFM spintronics.