Anomalous Near-Field Heat Transfer between a Cylinder and a Perforated Surface

We predict that the near-field radiative heat-transfer rate between a cylinder and a perforated surface depends nonmonotonically on their separation. This anomalous behavior, which arises due to evanescent-wave effects, is explained using a heuristic model based on the interaction of a dipole with a plate. We show that nonmonotonicity depends not only on geometry and temperature but also on material dispersion—for micron and submicron objects, nonmonotonicity is present in polar dielectrics but absent in metals with small skin depths.

Figure 1

Heat-transfer rate $H$ from a room-temperature ring to a cylinder (or sphere) of fixed radius $R=0.1\mu \mathrm{m}$ and aspect ratio $\Lambda =L/2R$ held at $T=0$, as a function of their center-center separation $d$. $H$ is normalized by the heat radiation of the isolated ring $H_r$. Both objects are lossy dielectrics with $\mathrm{Re}\epsilon \approx 12$ (see text). Inset shows the flux spectrum $\Phi (\omega )$ of the $\Lambda =5$ configuration at three separations, and also of the isolated cylinder and ring (dashed lines).

Figure 2

Heat-transfer rate $H$ between the ring and cylinder of Fig. 1, for fixed cylinder aspect ratio $\Lambda =5$ and thin ring thickness $h=5\times {10}^{-3}D$, as a function of $d$ and for multiple cylinder lengths $L$. $H$ is normalized by the radiation of the isolated ring $H_r$ multiplied by the cylinder area $A_c$. The shaded region denotes separations over which the two objects are interleaved. Top inset shows the critical separation $d_c$ of largest $H$ as a function of $L$, with shaded areas again denoting interleaved configurations. Bottom inset shows $H$ (solid lines) along with $\mathrm{Im}{G}_{ii}$ at the cylinder location (dashed lines) in the limit $h$, $R$, $L\to 0$, as computed by a heuristic model (see text).

Figure 3

Heat-transfer rate $H$ between the ring and cylinder of Fig. 1, for fixed cylinder aspect ratio $\Lambda =5$, as a function of separation $d$. $H$ is normalized to the radiation rate of the isolated ring $H_r$, and plotted for multiple material configurations. Insets show the corresponding flux spectra $\Phi (\omega )$ at three different (labeled) separations.