Coherent transport from molecular dynamics simulations
Tobias Spitaler
11:15 - 12:15 Wednesday 18 March 2020 PH01150 Video recording: mp4
Phonon transport in bulk materials is usually described by a diffusive picture. At nanoscale lengths, boundaries and interfaces play an important role. The transport can become ‘ballistic’, when the phonon mean free path is larger than the length a phonon travels before meeting a boundary. In the ballistic regime phonons can be scattered diffusively or be reflected specularly (coherently) at interfaces. Phonons with a wavelength in the order of the structure sizes are scattered coherently which is a manifestation of the wave-like nature of the phonons. This phonon coherence creates phonon band gaps and alters the phonon dispersion relation. Materials which show coherence effects have potential applications in thermo-optics, thermoelectrics, as sources, filters, detectors of phonons, heat-waveguides and more.
Superlattices are promising candidates for showing coherence effects and are good model systems to study the coherence effects as the layer thickness can be altered.
Computer simulations are used to design candidates which show significant coherence effects.
The dynamics of the atoms within superlattices in equilibrium is simulated using classical molecular dynamics. The equilibrium fluctuations of the atomic velocities are tracked throughout the simulation and their correlations provide information for extracting the coherence length. The methods used and the results for GaN/InN superlattices will be presented.
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Institute of Solid State Physics
