Article

# Surface Phonon Polaritons Mediated Energy Transfer between Nanoscale Gaps

Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
(Impact Factor: 13.59). 09/2009; 9(8):2909-13. DOI: 10.1021/nl901208v
Source: PubMed

ABSTRACT

Surface phonon polaritons are electromagnetic waves that propagate along the interfaces of polar dielectrics and exhibit a large local-field enhancement near the interfaces at infrared frequencies. Theoretical calculations show that such surface waves can lead to breakdown of the Planck's blackbody radiation law in the near field. Here, we experimentally demonstrate that surface phonon polaritons dramatically enhance energy transfer between two surfaces at small gaps by measuring radiation heat transfer between a microsphere and a flat surface down to 30 nm separation. The corresponding heat transfer coefficients at nanoscale gaps are 3 orders of magnitude larger than that of the blackbody radiation limit. The high energy flux can be exploited to develop new radiative cooling and thermophotovoltaic technologies.

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Available from: Arvind Narayanaswamy, Oct 26, 2014
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• "Nanoscale radiative heat transfer has attracted a lot of attention in the last few years because of Polder and van Hove's prediction [1] on the possibility to observe heat fluxes at subwavelength distances which are several orders of magnitude larger than those obtained by the blackbody theory. Recent experimental results [2] [3] [4] [5] [6] [7] [8] [9] have confirmed these theoretical predictions [1] [10] [11]. "
##### Article: Radiative heat flux predictions in hyperbolic metamaterials
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ABSTRACT: The transport of heat mediated by thermal photons in hyperbolic multilayer metamaterials is studied using the fluctuational electrodynamics theory. We discuss the dependence of the attenuation length and the heat flux on the design parameters of the multilayer structure. We demonstrate that in comparison to bulk materials the flux inside layered hyperbolic materials can be transported at much longer distances, making these media very promising for thermal management and for near-field energy harvesting.
Full-text · Article · Jun 2015 · Journal of Quantitative Spectroscopy and Radiative Transfer
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• "All rights reserved. configurations clearly showed the evidence of ehnhancement of radiative transfer due to near-field effects above the Planck limit [10] [11] [12] [13] [14] [15] [16] [17]. An accurate modeling of nano- TPV energy conversion systems through the solution of the coupled near-field thermal radiation, charge and heat transport problem was provided by Francoeur et al. [18]. "
##### Dataset: Near-Field Thermal Emission between Corrugated Surfaces Separated by Nano-Gaps

Full-text · Dataset · Apr 2015
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• "Although the possibility of enhancements beyond the black-body limit was realized in the 1950s [1] [2], efforts to find underlying limits remain restricted to planar structures (including effective-medium metamaterials) [20, 25, 36–38]. Moreover, heat-transfer calculations have been carried out only in a handful of geometries, including planar bodies with translational symmetry [8–27], simple sphere–sphere [39] and sphere–plate [40] [41] [42] [43] configurations and more recently, complex shapes [32, 44–47] that can be studied computationally. We propose that the quantities limiting near-field heat exchange are the polarization currents within the bodies. "
##### Article: Shape-Independent Limits to Near-Field Radiative Heat Transfer
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ABSTRACT: We derive shape-independent limits to the spectral radiative heat-transfer rate between two closely spaced bodies, generalizing the concept of a black body to the case of near-field energy transfer. By conservation of energy, we show that each body of susceptibility $\chi$ can emit and absorb radiation at enhanced rates bounded by $|\chi|^2 / \operatorname{Im} \chi$, optimally mediated by near-field photon transfer proportional to $1/d^2$ across a separation distance $d$. Dipole--dipole and dipole--plate structures approach restricted versions of the limit, but common large-area structures do not exhibit the material enhancement factor and thus fall short of the general limit. By contrast, we find that particle arrays interacting in an idealized Born approximation exhibit both enhancement factors, suggesting the possibility of orders-of-magnitude improvement beyond previous designs and the potential for radiative heat transfer to be comparable to conductive heat transfer through air at room temperature, and significantly greater at higher temperatures.
Full-text · Article · Apr 2015 · Physical Review Letters