Bipolar Thermoelectric Josephson Engine

The direct conversion of a thermal gradient into an electrical power, known as thermoelectric effect, was considered impossible in pristine superconductors due to the perfect particle-hole symmetry around the Fermi surface. Linear thermoelectric phenomena in superconducting systems were obtained only by explicitly breaking the particle-hole symmetry [Ref. 1-3].

Recently, we have predicted [Ref. 4], and, then, experimentally demonstrated [Ref. 5] that a superconducting tunnel junction can develop bipolar thermoelectric effects in the presence of a large thermal gradient due to spontaneous particle–hole symmetry breaking. The junction, integrated in a Josephson interferometer to fully suppress the dissipationless Cooper pairs current, generates a thermovoltage up to ±150 μV. The corresponding non-linear Seebeck coefficient is around , which is comparable with quantum dots performance and ~10⁵ times larger than the value expected for normal metals at subkelvin temperatures. Furthermore, we will present a Bipolar Thermoelectric Josephson Engine able to generate phase-tunable electric powers up to ~140 nW mm^–2 [Ref. 5].

Applications in superconducting quantum technology as power generators, memories, radiation sensors and switches will be discussed.