1 research outputs found
Mixed superconducting state without applied magnetic field
A superconducting (SC) mixed state occurs in type-II superconductors where
the upper critical field Hc2 is higher than the thermodynamic critical field
Hc. When an applied field is in between these fields, the free energy depends
weakly on the order parameter which therefore can be small (SC state) or zero
(normal state) at different parts of the sample. In this paper we demonstrate
how a normal state along a line traversing a superconductor can be turned on
and off externally in zero field. The concept is based on a long,
current-carrying excitation coil, piercing a ringshaped superconductor. The
ring experiences zero field, but the vector potential produced by the coil
generates a circular current that destroys superconductivity along a radial
line starting at preexisting nucleation points in the sample. Unlike the
destruction of superconductivity with magnetic field, the vector potential
method is reversible and reproducible; full superconductivity is recovered upon
removing the current from the coil, and different cooldowns yield the same
normal lines. We suggest potential applications of this magnetic-field-free
mixed state.Comment: 5 pages, 7 figure