PD Dr. Svend-Age Biehs
Carl von Ossietzky Universität Oldenburg

Near-field heat transfer and persistent heat currents in non-reciprocal systems

The textbook laws of thermal radiation change significantly at the nanoscale due to the contribution of evanescent waves. As a consequence the transferred heat between two objects can surpass the blackbody limit by orders of magnitude when the separation distance is smaller than the thermal wavelength. This theoretical prediction made within the framework of fluctuational electrodynamics has been experimentally verified in recent years down to separation distances of only a few nanometers. However, there are still open fundamental questions in the extreme near-field regime for distances just before contact as well as regarding the impact of nonlocal effects for extremely thin transdimensional films.

In my presentation I will focus on the theory of radiative heat transfer in nanoscale many-body systems involving non-reciprocal materials. Such materials can be magneto-optical materials or Weyl semimetals, for instance. They share the property that, due to the broken time reversal symmetry, Lorentz reciprocity does not apply. For heat radiation this has interesting consequences. I will discuss in particular so-called persistent heat fluxes and persistent heat currents, the Hall effect for thermal radiation, the Feynman paradox induced by vacuum fluctuations, and the heat flux rectification via spin-spin coupling with non-reciprocal surface waves. If time permits, I will further discuss the possibility of non-reciprocal heat flux in quantum systems with synthetic fields.