Intertwined electronic and magnetic structure of the van-der-Waals antiferromagnet Fe2P2S6

Many unusual and promising properties have been reported recently for the transition metal trichalcogenides of the type M PS 3 ( M = V, Mn, Fe, Ni ...), such as maintaining magnetic order to the atomically thin limit, ultra-sharp many-body excitons, metal-insulator transitions and, especially for Fe 2 P 2 S 6 , giant linear dichroism among others. Here we conduct a detailed investigation of the electronic structure of Fe 2 P 2 S 6 using angle-resolved photoemission spectroscopy, q -dependent electron energy loss spectroscopy, optical spectroscopies and density functional theory. Fe 2 P 2 S 6 is a Mott insulator with a gap of E gap ≈ 1.4 eV and zigzag antiferromagnetism below T N = 119 K. The low energy excitations are dominated by Fe 3 d states. Large and sign-changing linear dichroism is observed. We provide a microscopic mechanism explaining key properties of the linear dichroism based on the correlated character of the electronic structure, thereby elucidating the nature of the spin-charge coupling in Fe 2 P 2 S 6 and related materials.