Berlin 2012 – scientific programme

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O: Fachverband Oberflächenphysik

O 85: Plasmonics and nanooptics V

O 85.9: Talk

Friday, March 30, 2012, 12:30–12:45, MA 005

Radiative cooling of nanoparticles close to a surface — •Maria Tschikin and Svend-Age Biehs — Institut für Physik, Carl von Ossietzky Universität Oldenburg, D-26111 Oldenburg

In the present work we investigate the radiative cooling of a heated nanoparticle immersed in a thermal bath close to a partially reflecting surface. In the long-wavelength limit the particle can be considered as a simple dipole that radiates like an antenna. The radiated power of the dipole with a given temperature is then found within the framework of fluctuating electrodynamics. It turns out that the radiated power of the particle is not only proportional to its polarizability but also to the electric and magnetic local density of states. Hence, the radiated power which will determine the thermal relaxation time of the nanoparticle is very sensitive to its environment similar to the lifetime of an excited atom. Now, in our calculations we first introduce a thermal relaxation time τ and compare the results for a metallic and a polar nanoparticle. We demonstrate an oscillating behavior of τ with respect to the separation distance from the surface, an analog of Friedel oscillations in Fermi liquids. In addition it can be shown, that the cooling rate strongly depends not only on the temperature difference between particle and environment, but also on the absolute temperature of the environment.