First-Principles Investigation on Phonon Mode Conversion of Thermal Transport in Silicene Under Tensile Strain

Based on the first-principles calculations of the phonon Boltzmann transport equation (pBTE) under the framework of the three-phonon scattering theory, we characterized the temperature and size dependence of the lattice thermal conductivity of monolayer silicene under the tensile strain. Our research shows that the lattice thermal conductivity of silicene has obvious strain dependence, and demonstrates the great potential of thermal management by applying strain in silicene. The TA phonon mode contributes the most to the thermal conductivity of silicene, while the contribution of the ZA phonon is suppressed. With the increase in tensile strain, the contribution of LA mode phonons to the thermal conductivity increases rapidly, and eventually become the dominant phonon mode of the silicene lattice thermal conductivity. We suspect that this phenomenon is caused by the reduction of the warpage of the silicene and the restoration of the crystal symmetry due to the tensile strain. When the characteristic size is less than 10 nm, the lattice thermal conductivity of silicene is no longer sensitive to temperature, and with the increase in tensile strain, the effective phonon mean free path (MFP) of silicene also increases, and the size effect is more obvious. The characterization of the scattering channel reveals its significant influence on the characteristics of thermal transport capacity of different phonon modes. These findings deepen the understanding of the phonon dynamics of the monolayer silicene-like structure, and provide the reference and theoretical basis for the research on the heat management of the corresponding material combined with strain and size and the development of thermal management technology.