Stable Neutral Atom Trap with a Thin Superconducting Disc

A stable magnetic quadrupole trap for neutral atoms on a superconducting Nb thin-film disc is demonstrated. The quadrupole field is composed of the magnetic field that is generated by vortices on the disc introduced by cooling the disc across the transition temperature with a finite field and an oppositely directed uniform field applied after cooling. The trap is stable when all trapping processes are performed above the dendritic instability temperature T(a). When the field intensity is changed below this temperature, the quadrupole field collapses and the trap disappears. The initial vortex density decreases even when the external field is changed at a temperature T > T(a). However, the vortex density is stabilized at an equilibrium density, whereas at T < T(a), it almost completely disappears. A stable trap can be formed, even when the initial vortices are introduced through a dendritic avalanche.