Vibrational Heat Transport in Molecular Junctions

TL;DR

This paper reviews vibrational heat transfer in molecular junctions, exploring how various factors influence thermal conduction mechanisms and effectiveness at the nanoscale, with emphasis on theoretical and experimental insights.

Contribution

It provides a comprehensive overview of current theoretical models and experimental findings on vibrational heat transport in molecular junctions, highlighting the role of anharmonicities and quantum effects.

Findings

System size, disorder, and structure significantly affect heat transfer mechanisms.

Quantum coherent effects can alter the efficiency of thermal conduction.

Techniques incorporating anharmonicities are essential for accurate modeling.

Abstract

We review studies of vibrational energy transfer in a molecular junction geometry, consisting of a molecule bridging two heat reservoirs, solids or large chemical compounds. This setup is of interest for applications in molecular electronics, thermoelectrics, and nanophononics, and for addressing basic questions in the theory of classical and quantum transport. Calculations show that system size, disorder, structure, dimensionality, internal anharmonicities, contact interaction, and quantum coherent effects, are factors that interplay to determine the predominant mechanism (ballistic/diffusive), effectiveness (poor/good) and functionality (linear/nonlinear) of thermal conduction at the nanoscale. We review recent experiments and relevant calculations of quantum heat transfer in molecular junctions. We recount the Landauer approach, appropriate for the study of elastic (harmonic) phononic transport, and outline techniques which incorporate molecular anharmonicities. Theoretical methods are described along with examples illustrating the challenge of reaching control over vibrational heat conduction in molecules.