Phonon transport across a vacuum gap separating intrinsic silicon crystals is predicted via the atomistic Green's function method combined with first-principles calculations of all interatomic force constants. The overlap of electron wave functions in the vacuum gap generates weak covalent interaction between the silicon surfaces, thus creating a pathway for phonons. Phonon transport, dominated by acoustic modes, exceeds near-field radiation for vacuum gaps smaller than ~ 1 nm. The first-principles-based approach proposed in this work is critical to accurately quantify the contribution of phonon transport to heat transfer in the extreme near field.
@article{arxiv.2110.14050,
title = {First-principles calculations of phonon transport across a vacuum gap},
author = {Takuro Tokunaga and Masao Arai and Kazuaki Kobayashi and Wataru Hayami and Shigeru Suehara and Takuma Shiga and Keunhan Park and Mathieu Francoeur},
journal= {arXiv preprint arXiv:2110.14050},
year = {2022}
}