Li Jincui, Weng Linxi, Xie Jie, Amrit Jay, Ramiere Aymeric
College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China.
Laboratoire Interdisciplinaire des Sciences du Numérique, CNRS, Université Paris-Saclay, Rue du Belvédère, 91405 Orsay, France.
Phys Rev E. 2022 Jun;105(6-1):064123. doi: 10.1103/PhysRevE.105.064123.
Phonon transport in square-cross-section nanowires is studied using spectral Monte Carlo simulations. Our results show the evolution of the different transport regimes described by Lévy statistics as a function of the surface roughness-to-thermal wavelength ratio σ/λ. More precisely, the relationship between the Lévy index γ describing the mean free path distribution Ψ(Λ) and σ/λ is established for the classical diffusive regime, the superdiffusive regime, and the ballistic regime in the nanowire. Besides the conventional superdiffusive regime that is marked by Ψ(Λ) with a single heavy-tailed peak, we reveal an unconventional superdiffusive subregime featuring Ψ(Λ) with sawtooth oscillations when σ/λ∼0.01. Investigation of the direction of propagation of phonons shows a significant narrowing of the angular distribution around the long axis of the nanowire due to the diffuse scattering at rough boundaries when σ/λ>0.1. These results shed light on the transport mechanisms of quasiballistic phonons and will help in nanowire design for specific applications.
