Coherent thermodynamics and transport properties of mesoscopic Josephson junctions

In this thesis, we focus on the physics of superconducting mesoscopic junctions and discuss their entangled thermal and electric properties. Due to the rich phenomenology of these systems, several applications have been realized, such as magnetometers, photo-detector, qubits, and others. We concentrate in particular on three research topics. The first topic concerns the equilibrium thermodynamics of a hybrid superconductor/normal metal junction. We study the microscopical statistical mechanism underlying the Maxwell relation between the supercurrent and the entropy of the junction. Then, we exploit these findings to build up a complete thermodynamic description based on thermodynamic processes and cycles involving supercurrent, temperature, condensate phase, and entropy. In the second topic of the thesis, we study the Peltier refrigeration of a superconductor/graphene device and its bolometric characteristics. We demonstrate that the low electron-phonon coupling and the low heat capacity in graphene allow reaching low base temperature and fast thermal response, respectively. Finally, the third topic consists of the nano-fabrication and characterization of a superconducting interferometer based on two gated constriction-junction. We demonstrate an unconventional relationship between the switching current and the gating field. A phenomenological theoretical model simulates the experimental results and suggests the existence of a coupling between phase and gating field.