Fine control of lattice thermal conductivity in low-dimensional materials

Abstract

Optimal regulation of lattice thermal conductivity in low-dimensional materials is fundamental to obtain highly efficient miniaturized devices. To this aim, we use quantum-mechanical based analyses to understand how atomic type and structural geometry determine electron density and lattice dynamic features ruling the thermal conduction. As a case study, we consider layered van der Waals transition metal dichalcogenides with a finite number of layers. We find that a large thermal conductivity is realized when the atomic bonds display highly covalent character, promoting fast motions of the cations in correspondence of the low-frequency phonon band. Such an effect is the result of the entangled electronic and phonon features, which are captured by the covalency and cophonicity metric. The investigation protocol that we present has general applicability and can be used to design novel thermal low-dimensional materials irrespective of the kind of atomic topology and chemical composition.