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.Managing and harvesting wasted heat in energy processes is becoming a big issue due to the limited energy resources and to the constraints of global warming. Heat can be transported by fluids and radiation, as well as guided in good conductors or devices, such as heat pipes. However, there exists no device that can manage the switching or heat amplification, as is the case in electricity.In the last century, electricity management and its use for logical operations have been realized through the development of two components: the diode [1] and the transistor [2]. By analogy, one can, of course, envisage developing similar thermal devices that could make the thermal control easier. Thus, one of the goals of recent researches in thermal science has been focused on thermal rectifiers, i.e. components which exhibit an asymmetric flux when the temperatures at their ends are inverted. Thermal rectifiers have been designed for phononic [3][4][5][6][7][8][9][10][11][12][13] and electronic [12,14] thermal transport, which has led to the conception and modeling of thermal transistors [15,16]. In the framework of thermal radiation, rectifiers have been the subject of numerous theoretical works, both in near field [17][18][19] and far field [20][21][22][23][24]. The most efficient of these devices have involved phase change materials, such as thermochrome [25] materials like VO 2 [26,27]. This has led to the design of radiative thermal transistors based on phase change materials too [28,29].The last two decades have also seen the emergence of individual quantum systems, such as classical atoms [30,31] or artificial ones, as is the case of quantum dots [32,33], which have been proposed to develop photon rectifiers [34][35][36], transistors [37,38] or even electrically controlled phonon transistors [39]. Moreover, given that quantum systems are always coupled to their environment, in particular to a thermal bath, the question of how heat is transferred through a set of quantum systems in interaction naturally arises [40][41][42] and has led to several studies reporting thermal rectification [43][44][45][46].The goal of this Letter is to demonstrate that a thermal transistor can be achieved with a quantum system, made of 3 two lev...

Daytime radiative cooling under sunlight can be achieved by reflecting solar irradiation and emitting infrared thermal radiation in the transparency regions of earth atmosphere. For the sake of aestheticism, control over coloration would be a clear added value for the automobile body or walls of a building. Since coloration decreases cooling performances because of solar absorption in the visible range, mitigating the loss in radiative cooling power requires selective narrowband absorption in the visible range. In order to make a compromise between aestheticism and energetic efficiency, we aim in this paper to obtain colored surfaces with mitigated sunlight absorption and high emission in the infrared. In this numerical study, we demonstrate that appropriate optical properties can be achieved with plasmonic core−shell nanoparticles (silica core, silver shell) and plain silver nanoparticles embedded in a silica and polydimethylsiloxane matrix. Spectral properties of the composites are obtained by Monte Carlo method. Varying the radii of the core and shell allows tuning the spectral position of the surface plasmon resonance, leading to different colors. It is possible to obtain multiple absorption peaks and therefore additional colors by mixing particles with different geometries. Eventually, increasing the volume fraction of nanoparticles leads to more vivid colors but also to a decrease of radiative cooling power. In conclusion, the structure that is proposed can be used for daytime radiative cooling with large control over the coloration.