Revisiting four-phonon scattering in phosphorene monolayer: A first-principle study

The influence of higher-order anharmonic effects on thermal transport in two-dimensional (2D) materials is increasingly recognized. Here, we investigate these effects in the phosphorene monolayer, a 2D material known for its excellent properties, to address the current lack of knowledge regarding its higher-order phonon anharmonicity. In this work, we have studied the impact of four-phonon scattering on the thermal transport of the phosphorene monolayer using first-principles calculations combined with the Boltzmann transport equation. It was found that the room-temperature thermal conductivity along the zigzag and armchair directions are reduced by ∼65% and ∼43%, respectively, compared to the results without considering four-phonon scattering, which reduces the thermal conductivity anisotropy ratio from 4.3 to 2.5. Acoustic phonons dominate in thermal transport, where there is three-phonon resonance scattering in the low-frequency range of 1.4–3.7 THz owing to the quasi-parallel behavior between in-plane transverse acoustic and out-of-plane acoustic branches along the G–X (Zigzag) direction. Meanwhile, including four-phonon scattering will cause the directional variation in phonon scattering rates, and the phonon group velocity serves as a scaling factor, amplifying the effect of four-phonon scattering on the thermal conductivity, which contribute to this variation in anisotropy. Our work reveals that the four-phonon interaction should be introduced to accurately describe the thermal transport properties of the phosphorene monolayer.