Quartic Anharmonic Lattice Thermal Conductivity in 2D InS Monolayer: Self-consistent Phonon Calculations

There are many reports on low lattice thermal conductivity in 2D van der Waal’s based materials for thermoelectric applications using Density Functional Theory (DFT) and Molecular Dynamics simulations. Wickramaratne [1] et. al. have extensively studied the excellent thermoelectric properties of 2D group III-VI materials such GaX and InX (X = S, Se) owing to the formation of ‘Mexican hat’ in the valence band of electronic structure. However, they have only focused on the electronic thermal conductivity and estimated the ZT using the upper-bound value of κl. This gap in research was motivation for several studies focusing on phonon transport and thermal properties of 2D InS monolayer. All the above reports are limited to the calculations of 1) phonon dispersion relations using the harmonic approximation and 2) lattice thermal conductivity using third order interatomic force constants (IFC’s) by solving BTE. However, a more reliable calculation of lattice transport properties and the effect of finite temperature on phonon spectra requires the inclusion of higher order anharmonicity. Self-consistent phonon theory based on quantum mechanical description of the phonons is an efficient non-perturbative way of including the anharmonicity. In this study, the above-mentioned approach is used to study the phonon transport properties and the thermodynamic parameters using quartic anharmonicity by including the quartic IFCs of InS monolayer to find their significant effect on the value of lattice thermal conductivity.

1. Wickramaratne, D., F. Zahid and R. K. Lake. "Electronic and thermoelectric properties of van der waals materials with ring-shaped valence bands." Journal of Applied Physics 118 (2015): 075101. 10.1063/1.4928559. https://doi.org/10.1063/1.4928559.