Molecular dynamics with quantum heat baths: results for nanoribbons and nanotubes

TL;DR

This paper develops a quantum molecular dynamics approach using quantum heat baths for thermal transport, compares it with nonequilibrium Green's function methods, and applies it to nanoribbons and nanotubes, revealing insights into quantum effects on thermal conductance.

Contribution

It introduces a generalized Langevin equation with quantum baths derived from NEGF, providing a new method for simulating quantum thermal transport in nanostructures.

Findings

Thermal conductance of graphene strips under strain is calculated.

Temperature dependence of carbon nanotubes' thermal transport is analyzed.

Quantum corrections to classical models are critically evaluated.

Abstract

A generalized Langevin equation with quantum baths (QMD) for thermal transport is derived with the help of nonequilibrium Green's function (NEGF) formulation. The exact relationship of the quasi-classical approximation to NEGF is demonstrated using Feynman diagrams of the nonlinear self energies. To leading order, the retarded self energies agree, but QMD and NEGF differ in lesser/greater self energies. An implementation for general systems using Cholesky decomposition of the correlated noises is discussed. Some means of stabilizing the dynamics are given. Thermal conductance results for graphene strips under strain and temperature dependence of carbon nanotubes are presented. The "quantum correction" method is critically examined.