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Energy Transport by Radiation in Hyperbolic Material Comparable to Conduction
Author(s) -
Salihoglu Hakan,
Iyer Vasudevan,
Taniguchi Takashi,
Watanabe Kenji,
Ye Peide D.,
Xu Xianfan
Publication year - 2020
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201905830
Subject(s) - thermal conduction , materials science , phonon , thermal radiation , radiative transfer , heat transfer , thermal conductivity , condensed matter physics , work (physics) , radiant energy , radiation , mechanics , thermodynamics , optics , physics , composite material
Radiation as a heat transfer mode inside a bulk material is usually negligible in comparison to conduction. Here, the contribution of radiation to energy transport inside a hyperbolic material, hexagonal boron nitride (hBN), is investigated. With hyperbolic dispersion, i.e., opposite signs of dielectric components along principal directions, phonon polaritons contribute significantly to energy transport due to a much greater number of propagating modes compared to that in a normal material. A many‐body model is developed to account for radiative heat transfer in a material with a nonuniform temperature distribution. The total radiative heat transfer through hBN is found to be largely contributed by the high‐κ modes within the Reststrahlen bands, and is comparable to phonon conduction. Experimental measurements of temperature‐dependent thermal transport also show that radiative contribution to thermal transport is of the same order as that from phonons. Therefore, this work shows, for the first time, radiative heat transfer inside a material can be comparable to phonon conductive heat transfer.