Acoustic Phonon Tunneling and Heat Transport due to Evanescent Electric Fields

TL;DR

This paper explores how acoustic phonons can tunnel through vacuum via evanescent electric fields enabled by piezoelectric coupling, leading to notable heat transfer between separated bodies.

Contribution

It introduces a mechanism for phonon tunneling through vacuum using evanescent electric fields, revealing a new pathway for heat conduction across gaps.

Findings

Phonons can tunnel through vacuum via evanescent electric fields.

Strong resonances can lead to near-unity phonon transmission.

Significant thermal conductance can occur across vacuum gaps.

Abstract

The authors describe how acoustic phonons can directly tunnel through vacuum and, therefore, transmit energy and conduct heat between bodies that are separated by a vacuum gap. This effect is enabled by introducing a coupling mechanism, such as piezoelectricity, that strongly couples electric field and lattice deformation. The electric field leaks into the vacuum as an evanescent field, which leads to finite solid-vacuum-solid transmission probability. Due to strong resonances in the system some phonons can go through the vacuum gap with (or close to) unity transmission, which leads to significant thermal conductance and heat flux.