Giant heat transfer in the crossover regime between conduction and radiation

• Published in: Nature communications Vol. 8; no. 1; pp. 1 - 5
• Main Authors: Kloppstech, Konstantin, Könne, Nils, Biehs, Svend-Age, Rodriguez, Alejandro W., Worbes, Ludwig, Hellmann, David, Kittel, Achim
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 15-02-2017; Nature Publishing Group; Nature Portfolio
• Subjects: 639/624/1111/1116; 639/624/400/1021; 639/925/929/353; Electron microscopes; Heat transfer; Humanities and Social Sciences; multidisciplinary; Radiation; Science; Temperature
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms14475

Heat is transferred by radiation between two well-separated bodies at temperatures of finite difference in vacuum. At large distances the heat transfer can be described by black body radiation, at shorter distances evanescent modes start to contribute, and at separations comparable to inter-atomic spacing the transition to heat conduction should take place. We report on quantitative measurements of the near-field mediated heat flux between a gold coated near-field scanning thermal microscope tip and a planar gold sample at nanometre distances of 0.2–7 nm. We find an extraordinary large heat flux which is more than five orders of magnitude larger than black body radiation and four orders of magnitude larger than the values predicted by conventional theory of fluctuational electrodynamics. Different theories of phonon tunnelling are not able to describe the observations in a satisfactory way. The findings demand modified or even new models of heat transfer across vacuum gaps at nanometre distances.
Kloppstech
et al
. report experimental observations of the heat transfer between a gold tip and an atomically flat gold sample in the 0.2–7 nm regime. The observed flux rates are four orders of magnitude larger than expected from theory, suggesting the possibility of additional heat transfer mechanisms.