Anharmonic phonon renormalization assisted acoustic branch scattering induces ultralow thermal conductivity and high thermoelectric performance of 2D SnSe

Abstract

Using the full electron-phonon couplings calculation, the effect of anharmonic phonon renormalization, electron-phonon interaction, and mean-free-path filtering on the transport property of 2D SnSe are systematically studied. The self-consistent phonon theory is used to deal with the inherent soft mode by anharmonic phonon renormalization. The anharmonic phonon renormalization reduces the gap between the acoustic branch and optical branch, enhancing the four-phonon scattering and reducing the lattice thermal conductivity. Under electron-phonon interaction and mean-free-path filtering, the lattice thermal conductivity further decreases from 0.3 W/mK to 0.15 W/mK at 800 K. As a result, the maximum ZT value (about 4.4) shows almost two times larger than ZT value (about 2.3) without interaction. Considering simultaneously the effect of anharmonic phonon renormalization, electron-phonon interaction, and mean-free-path filtering, our work not only provides an accurate prediction of transport property, but also exhibits a computational framework for thermoelectric materials.