Heat diode effect and negative differential thermal conductance across nanoscale metal-dielectric interfaces

Controlling heat flow by phononic nanodevices has received significant attention recently because of its fundamental and practical implications. Elementary phononic devices such as thermal rectifiers, transistors, and logic gates are essentially based on two intriguing properties: heat diode effect and negative differential thermal conductance. However, little is known about these heat transfer properties across metal-dielectric interfaces, especially at nanoscale. Here we analytically resolve the microscopic mechanism of the nonequilibrium nanoscale energy transfer across metal-dielectric interfaces, where the inelastic electron-phonon scattering directly assists the energy exchange. We demonstrate the emergence of heat diode effect and negative differential thermal conductance in nanoscale interfaces and explain why these novel thermal properties are usually absent in bulk metal-dielectric interfaces. These results will generate exciting prospects for the nanoscale interfacial energy transfer, which should have important implications in designing hybrid circuits for efficient thermal control and open up potential applications in thermal energy harvesting with low-dimensional nanodevices.

Figure 1

Sketch of inelastic scattering due to the e-ph interaction across the metal-dielectric interface. (a) Down scattering of electrons with losing energy accompanied by phonon emission. (b) Up scattering of electrons with gaining energy accompanied by phonon absorption.

Figure 2

Heat diode effect and NDTC in the two-level interface system. (a) Sketch of the two-level system setup describing the nanoscale metal-dielectric interface. (b) Heat flux $J$ as a function of the fermionic temperature $T_L$ and the bosonic temperature $T_R$. Parameters are ${\Gamma }_L={\Gamma }_R=2.5$ meV$/\hslash$, ${\varepsilon }_1=25$ meV, ${\omega }_0=50$ meV. (c) The rectification ratio as a function of $T_0$ for $T_L=T_0\pm \Delta T/2$, $T_R=T_0\mp \Delta T/2$ with $\Delta T=30$ K. Inset depicts the rectification ratio as a function of the lower level energy at $T_0=200$ K and $\Delta T=30$ K. Other parameters are the same as above. (d) Heat flux vs $\Delta T$ along three corresponding lines in (b): (i) $T_L=T_0+\Delta T$, $T_R=T_0-\Delta T$; (ii) $T_L=T_0+\Delta T,T_R=T_0$; (iii) $T_L=T_0,T_R=T_0-\Delta T$, with $T_0=300$ K.