We demonstrate that a thermal transistor can be made up with a quantum system of three 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 by determining the heat fluxes by means of the strong-coupling formalism. For the case of three interacting spins, in which one of them is coupled to the other two, 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 nanosystems.

We demonstrate that two interacting spinlike systems characterized by different excitation frequencies and coupled to a thermal bath each, can be used as a quantum thermal diode capable of efficiently rectifying the heat current. This is done by deriving analytical expressions for both the heat current and rectification factor of the diode, based on the solution of a master equation for the density matrix. Higher rectification factors are obtained for lower heat currents, whose magnitude takes their maximum values for a given interaction coupling proportional to the temperature of the hotter thermal bath. It is shown that the rectification ability of the diode increases with the excitation frequencies difference, which drives the asymmetry of the heat current, when the temperatures of the thermal baths are inverted. Furthermore, explicit conditions for the optimization of the rectification factor and heat current are explicitly found.

Surface electromagnetic waves double thermal conductivity of thin SiN membranes.

Based on Bruggeman's symmetric effective-medium formula and an explicit expression derived for the temperature evolution of the volume fractions of the metallic and isolating domains appearing during the heating and cooling of ${\mathrm{VO}}_2$, respectively, we develop a model to describe the hysteresis of its electrical and thermal conductivities as well as of its specific heat capacity. The model takes into account the average value and standard deviation of the transition temperatures of the individual domains, as well as their activation energies, which represent the driving force for the existence of the ${\mathrm{VO}}_2$ hysteresis. It is shown that the model's predictions driven by these three parameters related to the microstructure of ${\mathrm{VO}}_2$ are in good agreement with robust experimental data. Furthermore, as these parameters are intrinsically correlated to the doping, defect, strain, and interface effects of ${\mathrm{VO}}_2$, the proposed model enables the seamless integration of these effects, and therefore, its predictions are also expected to be useful for describing the thermal and electrical properties of composites based on ${\mathrm{VO}}_2$.

Based on the thermal hysteresis of a phase change material exchanging radiative heat with a phase invariable one, we propose a radiative thermal memristor characterized by a Lissajous curve between their exchanged heat flux and temperature difference periodically modulated in time. For a memristor with terminals of ${\mathrm{VO}}_2$ and a blackbody, it is shown that (i) the temperature variations of its memristance follow a closed loop determined by the thermal hysteresis width of ${\mathrm{VO}}_2$, and (ii) the thermal memristance on-off ratio is determined by the contrast of ${\mathrm{VO}}_2$ emissivities for its insulating and metallic phases and is equal to 3.6. The analogy of the proposed memristor to its electrical counterpart makes it promising to lay the foundations of the thermal computing with photons.