Theoretical Investigation of Auger and Electron–Surface Optical Phonon Processes near the K-Points in Monolayer PtSe2 and PtS2 on Polar Dielectric Substrates

In this work, we present a theoretical investigation of electron–surface optical phonon (SOP) interactions and Auger recombination processes in monolayer PtSe2 and PtS2 supported on polar dielectric substrates such as SiO2 and hBN. The analysis is based on a low-energy effective Hamiltonian describing the electronic structure near the K and K′ valleys of the Brillouin zone, combined with the Fröhlich interaction model to account for the coupling between charge carriers and substrate-induced optical phonons. The comparison between Auger recombination and SOP scattering is performed at a representative carrier density of n=1012 cm−2 within the investigated temperature range. We analyze the formation of polaronic states arising from the hybridization between electronic excitations and SOPs and evaluate the associated Rabi splitting energies and oscillator strengths. The temperature dependence of the SOP-induced scattering rates and the influence of the monolayer–substrate separation on carrier–phonon interactions are also examined. Our results show that electron–phonon coupling strongly depends on the dielectric properties of the supporting substrate, with larger anticrossing gaps predicted for hBN-supported structures compared with SiO2-supported systems. Auger recombination constitutes the dominant carrier relaxation channel within the investigated temperature range, whereas SOP scattering becomes increasingly significant at elevated temperatures, where both mechanisms approach a comparable inelastic phonon-limited regime. These findings highlight the role of dielectric engineering in controlling carrier relaxation dynamics in Pt-based TMDC heterostructures.