Modeling of second sound in carbon nanostructures

TL;DR

This paper investigates phonon transport and the phenomenon of second sound in low-dimensional carbon nanostructures using semi-classical molecular dynamics simulations, revealing temperature-dependent hydrodynamic behavior and specific velocity characteristics.

Contribution

It introduces a quantum-statistics-aware numerical modeling approach for second sound in 2D carbon structures and identifies the conditions under which hydrodynamic effects occur.

Findings

Second sound velocity is approximately 6 km/s.

Hydrodynamic effects diminish above 200K.

Stronger hydrodynamic effects observed in carbon nanotubes.

Abstract

The study of thermal transport in low-dimensional materials has attracted a lot of attention recently after discovery of high thermal conductivity of graphene. Here we study numerically phonon transport in low-dimensional carbon structures being interested in the hydrodynamic regime revealed through the observation of second sound. We demonstrate that correct numerical modeling of such two-dimensional systems requires semi-classical molecular dynamics simulations of temperature waves that take into account quantum statistics of thermalized phonons. We reveal that second sound can be attributed to the maximum group velocity of bending optical oscillations of carbon structures, and the hydrodynamic effects disappear for $T>200$K, being replaced by diffusive dynamics of thermal waves. Our numerical results suggest that the velocity of second sound in such low-dimensional structures is about 6 km/s, and the hydrodynamic effects are manifested stronger in carbon nanotubes rather than in carbon nanoribbons.