Exploring hot carrier relaxation dynamics in MoSi2N4 monolayer for photocatalytic applications: Insights into electron-phonon coupling mechanisms

Abstract

The relaxation process of hot carriers in MoSi2N4 monolayer remains unclear due to the need to sample electron–phonon interaction at different momenta. Utilizing density functional theory (DFT) combined with nonadiabatic molecular dynamics (NAMD), we determined that the material possesses an indirect bandgap of approximately 2.33 eV, primarily originating from the d orbitals of inner Mo atoms. NAMD simulations unveil rapid relaxation of hot electrons and holes, exhibiting lifetimes of approximately 166 fs and 146 fs, respectively. The rapid relaxation of hot carriers couples with the vibrations of outer Si and N atoms, with no inter-valley scattering observed between the K and K′ valleys. Notably, the coupling between the d orbitals of inner Mo atoms and the vibrations of outer Si and N atoms plays a pivotal role in determining the relaxation dynamics of hot carriers, shedding light on the intricate interplay between electronic and vibrational modes in this material. Our research reveals the potential application value of MoSi2N4 monolayer material as a photocatalyst and elucidates a relaxation mechanism governing the dynamics of excited carriers.