Ex-situ modification of lattice thermal transport through coherent and incoherent heat baths

T Ma and Y Wang, MATERIALS TODAY PHYSICS, 29, 100884 (2022).

DOI: 10.1016/j.mtphys.2022.100884

Most of the current strategies for tailoring the thermal conductivity of materials directly modify the composition or structure of a material, for instance, by alloying or modifying the microstructure. In this work, we demonstrate the ex-situ modification of thermal conductivity of devices containing secondary periodicity through the rational choice of heat baths. Molecular dynamics simulations show that coherent baths, of which the phonon trans-mission spectrum matches with that of the device, can greatly increase the thermal conductivity of Lennard-Jones (up to 400%) and silicon/germanium (up to 40%) superlattice devices, when compared with the cases of incoherent baths. Phonon transmission calculations reveal strong coherent-incoherent phonon nonequilibrium near the interface between the device and incoherent baths, which, as elucidated by a proposed coherent-incoherent phonon transport model, hinders thermal transport. This work provides a strategy to greatly tailor the thermal conductivity of nanodevices ex-situ without the need to irreversibly modify the structure or composition of the device.

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