Exciton dynamics, Fano quantum interference and d-d excitation in the single crystal of two-dimensional antiferromagnetic Fe2P2S6

Abstract

Excitonic quasiparticle and their interactions with phonons, magnons and charge carriers may play a pivotal role in governing the optical properties and their correlation with magnetic interactions in two-dimensional (2D) magnetic semiconductors. Further, in transition metal compounds, d-d electronic transitions, arising from excitations between crystal-field split d-orbitals, significantly influence the optical and magnetic properties, particularly in strongly correlated and low-dimensional systems. Fe2P2S6, a layered antiferromagnetic semiconductor, offers a rich platform for studying the interplay between spin, charge, and lattice degrees of freedom in these 2D systems. In this work, we investigate the photoluminescence (PL) properties of Fe2P2S6 to probe the exciton dynamics, intra-atomic transitions, and their temperature evolution. Two prominent d-d emission peaks are observed at ~ 1.63 eV (D1) and ~ 1.80 eV (D2), attributed to the crystal field-split Fe2+ states. An excitonic emission near the band edge is also identified, which exhibits a characteristic Fano asymmetric line shape. This asymmetry is attributed to the quantum interference between the discrete excitonic state and the d-d transition induced continuum (D2), revealing a Fano resonance behaviour. This exciton peak disappears well before the Neel temperature, indicating its faster destabilization than magnetic ordering. Temperature-dependent PL measurements show a quenching of the excitonic peak with increasing temperature. Our findings provide detailed insight into the optical excitation pathways in Fe2P2S6.