Tuning dimensionality, magnetism and conduction in van-der-Waals Mott insulators*

We report discovery of new metallic and magnetic phases in the van-der-Waals antiferromagnets MPS₃, where M = Transition Metal, form an ideal playground for tuning both low-dimensional magnetic and electronic properties[1-4]. These are layered honeycomb antiferromagnetic Mott insulators, long studied as near-ideal 2D magnetic systems with a rich variety of magnetic and electric properties across the family.
We will present magnetic, structural and electrical transport results and compare the behaviour of Fe-, V-, Mn- and NiPS₃ as we tune them towards 3D structures – and Mott transitions from insulator to metal. I will show recent results on record high-pressure neutron scattering, which has unveiled an enigmatic form of short-range magnetic order in metallic FePS₃.
We have mapped out the full phase diagram - a first in this crucial family of materials. We observe multiple transitions and new states, and an overall increase in dimensionality and associated changes in behaviour.
[1] G. Ouvrard et al., Mat. Res. Bull., 1985, 20, 1181.
[2] C.R.S. Haines et al., Phys. Rev. Lett. 2018, 121, 266801.
[3] M.J. Coak et al., J.Phys.:Cond. Mat. 2019, 32, 124003.
[4] M.J. Coak et al., Phys. Rev. X, forthcoming