Phonon thermal transport in Janus single layer M2XY (M = Ga; X, Y = S, Se, Te): A study based on first-principles

Based on the first-principles calculations, we introduced several stable 2D Janus single layer materials (Ga2SSe, Ga2STe, Ga2SeTe) and carried out a series of thermal transport studies of them. Ga2STe and Ga2SeTe are belong to the direct band-gap semiconductors while the Ga2SSe is indirect band-gap semiconductor. The calculated lattice thermal conductivity IQ is arranged in the sequence of Ga2SSe > Ga2SeTe > Ga2STe, and in the room temperature the corresponding values are 26.16 W m(-1) K-1, 11.98 W m(-1) K-1 and 15.72 W m(-1) K-1 for monolayer Ga2SSe, Ga2STe and Ga2SeTe, respectively, the optical modes have the smallest contributions to the lattice thermal conductivity. For the purpose of application in the thermoelectric field, which can be further reduced by adjust sample size appropriately. Ga2STe has a similar phonon group velocity with Ga2SeTe, the larger scattering rates caused the smaller lattice thermal conductivity of it. By studying the thermal transport of different phonon modes we found an unusual relationship between the anharmonic scattering rates and the weighted phase space W. The above researches demonstrate a range of thermoelectric properties of these 2D Janus single layer materials and lay the foundation for their better applications in the thermoelectric field.