Maximal near-field radiative heat transfer between two plates

A parametric study of Drude and Lorentz models performances in maximizing near-field radiative heat transfer between two semi-infinite planes separated by nanometric distances at room temperature is presented in this paper. Optimal parameters of these models that provide optical properties maximizing the radiative heat flux are reported and compared to real materials usually considered in similar studies, silicon carbide and heavily doped silicon in this case. Results are obtained by exact and approximate (in the extreme near-field regime and the electrostatic limit hypothesis) calculations. The two methods are compared in terms of accuracy and CPU resources consumption. Their differences are explained according to a mesoscopic description of near-field radiative heat transfer. Finally, the frequently assumed hypothesis which states a maximal radiative heat transfer when the two semi-infinite planes are of identical materials is numerically confirmed. Its subsequent practical constraints are then discussed.Comment: 19 pages, 11 figures, submitted to Journal of Physics D : Applied Physic

A simple radiative thermal diode

We present a thermal rectification device concept based on far-field radiative exchange between two selective emitters. Rectification is achieved due to the fact that one of the selective emitters radiative properties are independent on temperature whereas the other emitter properties are strongly temperature dependent. A simple device constituted by two multilayer samples made of metallic (Au) and semiconductor (Si and HDSi) thin films is proposed. This device shows a rectification up to 70% with a temperature difference \Delta T = 200 K, a rectification ratio that has never been achieved so far with radiation-based rectifiers. Further optimization would allow larger rectification values. Presented results might be useful for energy conversion devices, smart radiative coolers / insulators engineering and thermal modulators development.Comment: 14 pages, 4 figure

Radiative thermal rectification using superconducting materials

Thermal rectification phenomenon is a manifestation of an asymmetry in the heat flux when the temperature difference between two interacting thermal reservoirs is reversed. In this letter, we present a far-field radiative thermal rectifier based on high temperature superconducting materials with a rectification ratio up to $80$. This value is among the highest reported in literature. Two configurations are examined : a superconductor (Tl$_2$Ba$_2$CaCu$_2$O$_8$) exchanging heat with 1) a black body and 2) another superconductor, YBa$_2$Cu$_3$O$_7$ in this case. The first configuration shows a higher maximal rectification ratio. Besides, we show that the two superconductors rectifier exhibits different rectification regimes depending on the choice of the reference temperature, i.e the temperature of the thermostat. Presented results might be useful for energy conversion devices, efficient cryogenic radiative insulators engineering and thermal logical circuits development.Comment: 5 pages, 4 figures, submitted to Applied Physics Letter

Quantum thermal transistor

We demonstrate that a thermal transistor can be made up with a quantum system of 3 interacting subsystems , coupled to a thermal reservoir each. This thermal transistor is analogous to an electronic bipolar one with the ability to control the thermal currents at the collector and at the emitter with the imposed thermal current at the base. This is achieved determining the heat fluxes by means of the strong-coupling formalism. For the case of 3 interacting spins, in which one of them is coupled to the other 2, that are not directly coupled, it is shown that high amplification can be obtained in a wide range of energy parameters and temperatures. The proposed quantum transistor could, in principle, be used to develop devices such as a thermal modulator and a thermal amplifier in nano systems.Comment: Physical Review Letters, American Physical Society, 2016, 116, pp.20060