Photoluminescent Quantum Interference in a van der Waals Magnet Preserved by Symmetry Breaking

Quantum interference gives rise to the asymmetric Fano resonance line shape when the final states of an electronic transition follow within a continuum of states and a discrete state, which has significant applications in optical switching and sensing. The resonant optical phenomena associated with the Fano resonance have been observed by absorption spectra, Raman spectra, transmission spectra, etc., but have rarely been reported in photoluminescence (PL) spectroscopy. In this work, we performed spectroscopic studies on layered chromium thiophosphate (CrPS4), a promising ternary antiferromagnetic semiconductor with PL in the near-infrared wavelength region and observed a Fano resonance when CrPS4 experiences phase transition into the antiferromagnetic state below the Neel temperature (38 K). The photoluminescence of the continuum states results from the d band transitions localized at Cr3+ ions, whereas the discrete state is formed by an impurity level, the electronic transition of which is enabled by symmetry breaking. Our findings provide insights into the photon-emitting coherent electronic transitions of CrPS4 and their connection to the magnetism-related broken symmetry.