Phonon Interference Effects in Molecular Junctions

TL;DR

This paper investigates how quantum interference in phonon transport through cross-conjugated molecules can significantly reduce thermal conductance, with implications for thermoelectric device design.

Contribution

It demonstrates the presence of destructive quantum interference effects in phonon transport in cross-conjugated molecules using first principles and Green's function methods.

Findings

Destructive interference reduces thermal conductance in cross-conjugated molecules.

Quantum interference effects are similar for phonons and electrons in these systems.

Chemical modifications can control thermal conductance in molecular junctions.

Abstract

We study coherent phonon transport through organic, \pi-conjugated molecules. Using first principles calculations and Green's function methods, we find that the phonon transmission function in cross-conjugated molecules, like meta-connected benzene, exhibits destructive quantum interference features very analogous to those observed theoretically and experimentally for electron transport in similar molecules. The destructive interference features observed in four different cross-conjugated molecules significantly reduce the thermal conductance with respect to linear conjugated analogues. Such control of the thermal conductance by chemical modifications could be important for thermoelectric applications of molecular junctions.