Comparative investigation of the thermal transport properties of Janus SnSSe and SnS₂monolayers

Recently, Janus two-dimensional (2D) materials as a new member of 2D derivatives have been receiving much attention due to their novel properties. In this work, the lattice thermal conductivity κL of the Janus SnSSe monolayer is investigated based on first-principles calculations, while that of the SnS2 monolayer is studied for comparison. It is found the the κL values of SnSSe and SnS2 are 13.3 and 11.0 W m-1 K-1 at room temperature, and acoustic branches dominate their thermal transport. Weaker phonon anharmonicity in SnSSe leads to a slightly higher κL, though it has weaker phonon harmonicity. The smaller Grüneisen parameters of TA and LA phonons lower than 1 THz in SnSSe indicate weaker phonon anharmonicity, resulting in a higher κL. Finally, the size effect and boundary effect are also investigated, exhibiting that the κL can further decrease at the nanoscale. Our work suggests that Janus SnSSe and SnS2 have a much lower κL compared with conventional transition metal dichalcogenides (TMDs) and are potential competitors in the thermoelectric field.