VERY LARGE THERMOPHASE IN FERROMAGNETIC JOSEPHSON JUNCTIONS

How temperature difference can create a large magnetic field.

In the early 19th century Thomas Seebeck showed that a magnetic needle deflects when two junctions of dissimilar metals in a loop are held at different temperatures. In this experiment, Seebeck first demonstrated a thermoelectric effect, where the temperature difference results into a small current whose magnetic field deflected the needle. Later in the 1940s Vitaly Ginzburg predicted that a similar effect can be produced more directly with superconductors. However, Ginzburg’s effect was tiny, and experiments conducted in the 1980s to demonstrate it are controversial. In the newly published work by Sebastian Bergeret from the Materials Physics Center in San Sebastian in collaboration with Francesco Giazotto (Italy) and Tero Heikkillä (Finland), it is  predicted how this effect can be amplified by many orders of magnitude via a combination of superconductors and ferromagnetic insulators realizing a hybrid Josephson junction. This effect is so large that it could be used for an extremely accurate sensors of radiation and thermometers.