  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.
