Tuning the thermal conductance of molecular junctions with interference effects

TL;DR

This study uses first-principles calculations to show how interference effects in molecular junctions can be tuned to control thermal conductance, aiding heat management in nanoscale devices.

Contribution

It demonstrates that substituents induce destructive interference in phonon transport, allowing thermal conductance tuning in single-molecule junctions.

Findings

Interference effects cause antiresonances in phonon transmission.

Substituent mass controls the energy position of antiresonances.

Thermal conductance can be significantly reduced via interference effects.

Abstract

We present an \emph{ab initio} study of the role of interference effects in the thermal conductance of single-molecule junctions. To be precise, using a first-principles transport method based on density functional theory, we analyze the coherent phonon transport in single-molecule junctions based on several benzene and oligo-phenylene-ethynylene derivatives. We show that the thermal conductance of these junctions can be tuned via the inclusion of substituents, which induces destructive interference effects and results in a decrease of the thermal conductance with respect to the unmodified molecules. In particular, we demonstrate that these interference effects manifest as antiresonances in the phonon transmission, whose energy positions can be controlled by varying the mass of the substituents. Our work provides clear strategies for the heat management in molecular junctions and more generally in nanostructured metal-organic hybrid systems, which are important to determine, how these systems can function as efficient energy-conversion devices such as thermoelectric generators and refrigerators.