Higher order anharmonicity and polymorphism in the lattice thermal conductivity of transition metal dichalcogenides

We present a comprehensive {\it ab initio} study of the effect of higher-order anharmonicity and polymorphism on the lattice thermal conductivity, $\mathit{\kappa }$, of single-layer transition metal dichalcogenides. We show that four-phonon processes are responsible for an additional suppression of $\mathit{\kappa }$ ranging from 15% to 35% in the ground-state 2H phase. Conversely, their effect is almost negligible on the thermodynamically competitive \1Tp\ phase. The $\mathit{\kappa }$ difference between the 2H higher-conductivity phase and the \1Tp\ lower-conductivity phase can be exploited for the design of thermal switches that may find applications in thermal management and in the development of phonon-based logic elements, particularly in the case of tellurides, where field-controlled ultrafast and reversible phase transitions have already been demonstrated experimentally.