Strong four-phonon scattering in monolayer and hydrogenated bilayer BAs with horizontal mirror symmetry

Recently, the important role of high-order anharmonic phonon-phonon interactions has been revealed in several materials, such as cubic boron arsenide (BAs), in which the wide phononic energy gap is found to be a critical factor causing the importance of four-phonon scattering. In this work, by solving the Boltzmann transport equation, we show that the four-phonon scattering has a significant impact on the thermal transport in honeycomb structured monolayer BAs (m-BAs) and its hydrogenated bilayer counterparts (bi-BAs). The lattice thermal conductivity (kappa(L)) values of all these structures are reduced after considering four-phonon scattering. Particularly, a huge drop in kappa(L) as large as 80% is observed for m-BAs compared to the case without four-phonon scattering, which is mainly caused by the suppression of phonon lifetimes. More interestingly, as opposed to the case of graphene, kappa(L) of m-BAs is abnormally lower than its bi-BAs counterparts, which is attributed to the much larger phonon scattering rate in m-BAs compared to that in bi-BAs. By further comparing BAs sheets with and without horizontal mirror symmetry, it is found that the contribution of flexural acoustic phonon exhibits most significant reduction in both mi-BAs and bi-BAs with horizontal mirror symmetry after including four-phonon scattering. This work provides physical understanding of the role of mirror symmetry and high-order phonon scattering on the thermal transport in two-dimensional materials. Published under an exclusive license by AIP Publishing.

Automated summary

Recently, the important role of high-order anharmonic phonon-phonon interactions has been revealed in several materials. By solving the Boltzmann transport equation, the significant impact of four-phonon scattering on thermal transport in honeycomb structured monolayer BAs and its hydrogenated bilayer counterparts has been shown. After considering four-phonon scattering, the lattice thermal conductivity of all these structures is reduced, especially for monolayer BAs, which shows a huge drop of 80% mainly due to the suppression of phonon lifetimes. In contrast to graphene, the thermal conductivity of monolayer BAs is abnormally lower than its bilayer counterparts, attributed to the much larger phonon scattering rate. The contribution of flexural acoustic phonon exhibits the most significant reduction in both monolayer and bilayer BAs with horizontal mirror symmetry after including four-phonon scattering.