Abstract
Artificial periodic nanostructures, known as phononic crystals, promise to control the thermal properties of nanostructures in the coherent regime, which can be achieved in semiconductors at low temperatures. Here, we study coherent thermal conduction in silicon nanowires with added periodic wings at sub-Kelvin temperature. Our simulations show that the added periodic wings flatten the phonon dispersion and thus reduce the thermal conductance. We investigate the dependence of this reduction on the size of the wings and conclude that the reduction is mainly caused by the periodicity of the wings, rather than by local resonances in them. These findings help to better understand the mechanisms controlling coherent heat conduction in periodic resonant nanostructures.
Highlights
Phononic crystals are a class of artificial metamaterials that aim to control phonon transport in the coherent regime [1,2]
Some authors [16] attributed this reduction in thermal conductivity to the coherent effects even at room temperature, while others [14] attributed it to the incoherent surface scattering of phonons at low temperatures
We demonstrate how the wings and their dimensions impact the thermal conductance of nanowires in the coherent regime and discuss the mechanisms of the observed reduction in the thermal conductance
Summary
Phononic crystals are a class of artificial metamaterials that aim to control phonon transport in the coherent regime [1,2]. The interference changes the phonon dispersion relation which determines thermal properties of the structure. Phononic crystals can control thermal properties of semiconductor nanostructures and find applications in heat conduction engineering [3]. Experiments have demonstrated that such heat conduction engineering is possible at low temperatures in membranes with two-dimensional arrays of holes [4,5].
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