Nonlinear thermoelectricity in superconducting tunnel junctions

Thermoelectric devices are of wide interest both from the theoretical side as basic heat engines/refrigerators and due to their potential applications for thermometry or radiation detection.
In the first part of this talk, I will discuss linear thermoelectric effects, which necessarily vanish in the presence of electron-hole (EH) symmetry. In a recent work, we showed how nonlinear effects could generate a new type of non-linear thermoelectricity even in the presence of EH symmetry. I will show an interesting example where thermoelectricity is induced in standard superconducting tunnel junctions. This result represents a novel mechanism. This is different from the linear thermoelectricity obtained by breaking electron-hole (EH) symmetry via a joint spin-splitting and spin-filtering mechanism which occurs in superconducting junctions done with ferromagnetic elements. In particular, the system shows comparable thermoelectric performances in the non-linear regime but with a state-of-art technology that does not require the manipulation of ferromagnetic insulator thin films. I will provide sufficient and general conditions for nonlinear thermoelectricity which are valid in the presence of EH symmetry but also well beyond the superconducting paradigm. Then I will discuss the connection of the effect with a spontaneous symmetry breaking of EH symmetry. Finally, I will present other applications such as thermoelectric switch/memories, thermoelectric relaxation oscillators and an initial design study of the possible experimental verification.

Fabio Taddei (9038) - fabio.taddei@nano.cnr.it
Stefan Heun (9472) - stefan.heun@nano.cnr.it