Correlated Excitonic Signatures in a Nanoscale van der Waals Antiferromagnet

Abstract

Composite quasi-particles with emergent functionalities in spintronic and quantum information science can be realized in correlated materials due to entangled charge, spin, orbital, and lattice degrees of freedom.1-3 Here we show that by reducing the lateral dimension of correlated antiferromagnet NiPS3 flakes to tens of nanometers, we can switch-off the bulk spin-orbit entangled exciton in the near-infrared (1.47 eV)4-6 and activate visible-range (1.8 – 2.2 eV) transitions with charge-transfer character. These ultra-sharp lines (<120 meV at 4.2 K) share the spin-correlated nature of the bulk exciton by displaying a Néel temperature dependent linear polarization. Furthermore, exciton photoluminescence lineshape analysis reveals a polaronic character via coupling with at-least 3 phonon modes and a comb-like Stark effect through discretization of charges in each layer. These findings augment the knowledge on the many-body nature of excitonic quasi-particles in correlated antiferromagnets and also establish the nanoscale platform as promising for maturing integrated magneto-optic devices.