Radiative Heat Shuttling

We demonstrate the existence of a shuttling effect for the radiative heat flux exchanged between two bodies separated by a vacuum gap when the chemical potential of photons or the temperature difference is modulated. We show that this modulation typically gives rise to a supplementary flux which superimposes to the flux produced by the mean gradient, enhancing the heat exchange. When the system displays a negative differential thermal resistance, however, the radiative shuttling contributes to insulate the two bodies from each other. These results pave the way for a novel strategy for an active management of radiative heat exchanges in nonequilibrium systems.

Figure 1

Sketch of a device displaying radiative heat shuttling. The system consists of two bodies separated by a vacuum gap of thickness $d$ that exchange an energy flux $J$ by means of thermal radiation. The intensive properties driving the heat transfer $X_L(t)$ and $X_R(t)$ are modulated in time.

Figure 2

Radiative heat shuttling between two thick ${\mathrm{SiO}}_2$ slabs when $T_L(t)=T_0+\delta T\sin (\mathrm{\Omega }t)$ and $T_R(t)=T_0$. The time average flux $\overline{J}$ is shown as a function of the separation distance $d$ for different values of the background temperature $T_0$. The amplitude of the oscillations is $\delta T=30\mathrm{K}$, and the modulation frequency $\mathrm{\Omega }$ is small with respect to the inverse of the thermalization time. In the inset, the averaged flux is computed by taking $T_R(t)=T_0+(\delta T/2)\sin (\mathrm{\Omega }t)$ (with the same parameter values).

Figure 3

Radiative heat shuttling between a direct-gap semiconductor (InSb) and a dielectric (${\mathrm{SiO}}_2$). The two materials are thermalized at the same temperature $T_0$, and the semiconductor is subject to an applied oscillating voltage $V_L(t)$. (a) Time-averaged heat flux $\overline{J}$ exchanged between the bodies as a function of the separation distance $d$. (b) Corresponding flux $J$ as a function of the chemical potential ${\mu }_L$ of the photons emitted by the semiconductor.

Figure 4

(a) Time-averaged flux $\overline{J}$ as a function of the separation $d$ between a ${\mathrm{VO}}_2$ slab and a sample of ${\mathrm{SiO}}_2$. The temperature of the ${\mathrm{VO}}_2$ slab is modulated as $T_L(t)=T_0+\delta T\sin (\mathrm{\Omega }t)$ with an amplitude $\delta T=30\mathrm{K}$, whereas the temperature of the other body is fixed at $T_R=T_0$. (b) Average flux $\overline{J}$ in this situation with respect to $T_0$. In the inset in (a), the modulus of the averaged flux ($\overline{J}$ is negative) is shown taking $T_R(t)=T_0+\delta T\sin (\mathrm{\Omega }t+\varphi )$ for different phases $\varphi$ and with the same parameter values.