Antiferromagnetic Z2 topological metal near the metal-insulator transition in MnS2

Antiferromagnetic (AFM) semiconductor MnS₂ 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 metallization 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 Z₂ 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 Z₂ topological invariant protected by the persisting combined time-reversal and half-translation symmetries. Such a topological phase was proposed theoretically by Mong et al. [Phys. Rev. B 81, 245209 (2010)] in 2010 for a system with AFM order on a fcc lattice, which until now has not been found in the pool of real materials. MnS₂ 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 MnS₂ as a candidate material for exploring magnetic topological phase transitions and for potential applications in AFM spintronics.