title: Giant heat transfer in the crossover regime between conduction and radiation.
abstract: 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.
authors.affiliation: Institute of Physics, Carl von Ossietzky University of Oldenburg, D-26111 Oldenburg, Germany.
authors.forename: Konstantin
authors.initials: K
authors.lastname: Kloppstech
authors.affiliation: Institute of Physics, Carl von Ossietzky University of Oldenburg, D-26111 Oldenburg, Germany.
authors.forename: Nils
authors.initials: N
authors.lastname: Könne
authors.affiliation: Institute of Physics, Carl von Ossietzky University of Oldenburg, D-26111 Oldenburg, Germany.
authors.forename: Svend-Age
authors.initials: SA
authors.lastname: Biehs
authors.affiliation: Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA.
authors.forename: Alejandro W
authors.initials: AW
authors.lastname: Rodriguez
authors.affiliation: Institute of Physics, Carl von Ossietzky University of Oldenburg, D-26111 Oldenburg, Germany.
authors.forename: Ludwig
authors.initials: L
authors.lastname: Worbes
authors.affiliation: Institute of Physics, Carl von Ossietzky University of Oldenburg, D-26111 Oldenburg, Germany.
authors.forename: David
authors.initials: D
authors.lastname: Hellmann
authors.affiliation: Institute of Physics, Carl von Ossietzky University of Oldenburg, D-26111 Oldenburg, Germany.
authors.forename: Achim
authors.initials: A
authors.lastname: Kittel