• transport
• thermodynamics
• solidstate
• mesoscopicphysics

Thermoelectricity is an important topic in mesoscopic physics, and has been lately investigated in low dimensional systems and quantum devices. The first inquiries on the response of superconductors to thermal gradients, instead, date back to the seminal article by Ginzburg. In principle, a thermoactive regime would be forbidden by the particle-hole (PH) symmetric structure of the spectrum of quasiparticle excitations of the superconducting state. Scattering theory in fact prescribes a null thermopower in case of PH symmetric systems. Actually, in order to induce thermoelectricity in superconducting or proximitized systems various strategies were proposed to break the PH symmetry, e.g. exploiting ferromagnetic correlations or nonlocal correlations enabled by the geometry of the devices.\par
In some recent works, a novel and simpler mechanism for the generation of a thermoelectric effect in Superconductor-Insulator-Superconductor (SIS') tunneling junctions was predicted. This mechanism is based on the spontaneous breaking of the PH symmetry, which occurs in SIS' junctions along with the application of a thermal bias to the junction. The PH symmetry in this case would be broken by an intrinsic effect, activated by the application of a finite temperature gradient. In the tunneling regime of the thermally biased junction, this effect strongly manifests at a value of the voltage bias corresponding to the matching peak of the two superconducting Densities Of States (DOSs).\par
Furthermore, it was demonstrated, by analytical investigations outlined in this recent research, that the effect relies on the locally monotonic decreasing nature of the superconducting DOS with energy, which, combined with a gapped state on the hotter electrode, leads to the generation of a nonlinear thermoelectric effect. Since just a gapped phase is required on the hot electrode, this led us to search for possible extensions of this effect in more general setups than the SIS' one. In the final part of my thesis work we extended the mechanism to other setups, using carbon based low-dimensional semiconductors (carbon nanotubes, graphene nanoribbons and bilayer graphene) on the hot electrode coupled to BCS superconductors on the cold one. We studied the highly nonlinear I-V characteristics of the resulting junctions and their thermoelectric figures of merit. Then we designed three different devices that could be used as thermoelectric elements in nanoelectronics. The performances predicted for the devices were notably high and we showed how they could be manipulated using the gating control.