Open AccessBallistic Phonons in Ultrathin Nanowires
Author(s) -
Daniel Vakulov,
Subash Gireesan,
Milo Yaro Swinkels,
Ruben Chavez,
Tom Vogelaar,
Pol Torres,
Alessio Campo,
Marta De Luca,
Marcel A. Verheijen,
Sebastian Koelling,
L. Gagliano,
J. E. M. Haverkort,
F. X. Álvarez,
P. A. Bobbert,
Ilaria Zardo,
Erik P. A. M. Bakkers
Publication year - 2020
Publication title -
nano letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.853
H-Index - 488
eISSN - 1530-6992
pISSN - 1530-6984
DOI - 10.1021/acs.nanolett.0c00320
Subject(s) - nanowire , phonon , ballistic conduction , condensed matter physics , heat current , mean free path , materials science , conductance , thermal conductivity , temperature gradient , fourier transform , mechanics , physics , nanotechnology , optics , composite material , scattering , quantum mechanics , electron
According to Fourier's law, a temperature difference across a material results in a linear temperature profile and a thermal conductance that decreases inversely proportional to the system length. These are the hallmarks of diffusive heat flow. Here, we report heat flow in ultrathin (25 nm) GaP nanowires in the absence of a temperature gradient within the wire and find that the heat conductance is independent of wire length. These observations deviate from Fourier's law and are direct proof of ballistic heat flow, persisting for wire lengths up to at least 15 μm at room temperature. When doubling the wire diameter, a remarkably sudden transition to diffusive heat flow is observed. The ballistic heat flow in the ultrathin wires can be modeled within Landauer's formalism by ballistic phonons with an extraordinarily long mean free path.
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