Gate tunable coherent heat transport : Study of the heat transfer in gate controlled hybrid superconducting systems

In recent decades, the scientific results of superconducting electronics have been remarkable. Observation of complex quantum phenomena, such as quantum coherence or manipulation of electronic quantum states, is nowadays commonplace. The thermal counterpart of superconductive electronics is the field of coherent caloritronics, which is used to control and manage heat transfer in superconducting circuits. Micro- and nano-structured superconductors are excellent laboratories for investigating and implementing low-temperature thermal manipulation architectures, primarily due to their unique density-of-states and coherence properties. Although this topic has been extensively studied in recent decades and several experimental and theoretical results have been achieved, flexible, scalable architectures for thermal transport management systems and reliable platforms for thermal energy manipulation remain missing. The lack of practical implementation of coherent caloritronic devices is primarily due to the need to utilize magnetic fields in all proposed architectures. This makes the devices less scalable and more complex, as is usually the case with magnetic fields.The purpose of our work is to pave the way for a real and scalable implementation of caloritronic architectures that leverage electrical fields. In fact, given the experience with CMOS transistors, it is evident that electrical fields are easier to generate and more scalable than magnetic fields, which require uncomfortable coils or flux lines. The fundamental structure used throughout this thesis is the top-gate architecture, consisting of a metallic electrode separated from the portion of the device where we want to apply the electric field by an insulating layer.This thesis consists of two main results: the first one refers to the generation of thermoelectricity with superconductors and its manipulation with the application of a gate potential; the second one refers to the photonic heat transfer due to electron-photon coupling in superconducting circuits, which we will show can be manipulated via a top gate. Both of these results had already been achieved using magnetic fields, rendering the proposed devices practically useless for real applications. We will show that to reach our results, we had to find new solutions and implement novel ideas to make the structures suitable for gate tuning.