Flux-induced Nernst effect in low-dimensional superconductors

Highlights: • The Nernst effect tells us that the presence of a magnetic field and a temperature gradient in a conductor yields a transverse voltage. • The Nernst effect in superconductors, especially above their critical temperature, has been a hot topic of research during the last decades. • I predict a new effect in which a transverse voltage arises, not because of the magnetic field, but rather because of the magnetic flux enclosed by a loop with non-uniform temperature. - Abstract: A method is available that enables consistent study of the stochastic behavior of a system that obeys purely diffusive evolution equations. This method has been applied to a superconducting loop with nonuniform temperature, with average temperature close to T_c. It is found that a flux-dependent average potential difference arises along the loop, proportional to the temperature gradient and most pronounced in the direction perpendicular to this gradient. The largest voltages were obtained for fluxes close to 0.3Φ₀, average temperatures slightly below the critical temperature, thermal coherence length of the order of the perimeter of the ring, BCS coherence length that is not negligible in comparison to the thermal coherence length, and short inelastic scattering time. This effect is entirely due to thermal fluctuations. It differs essentially from the usual Nernst effect in bulk superconductors, that is induced by magnetic field rather than by magnetic flux. We also study the effect of confinement in a 2D mesoscopic film.