Temperature dependent Raman and photoluminescence spectroscopy study of AgBiP₂Se₆

Transition metal thio- and seleno-phosphates are van der Waals materials, with an exciting promise to realize 2-dimensional (2D) physical models in the single layer limit. The quaternary compounds ABP₂X₆ (A,B are transition metals, P is phosphorous, X is sulfur or selenium), show evidence of ferro- and anti-ferroelectricity, as well as multiferroicity (magnetic). Among these, AgBiP₂Se₆ is a relatively new material that was theoretically predicted to exhibit anti-ferroelectricity near room temperature. In this talk, we present a detailed temperature-dependent Raman and photoluminescence (PL) spectroscopy study of bulk and exfoliated AgBiP₂Se₆ (down to few-nm thickness). We observe PL emission between 1.3-1.4 eV at low temperature. Anomalous changes in the temperature-dependent Raman and PL spectra and their implications on the thickness-dependent anti-ferroelectricity are discussed.