15 research outputs found
Quantum phase slip phenomenon in ultra-narrow superconducting nanorings
The smaller the system, typically - the higher is the impact of fluctuations.
In narrow superconducting wires sufficiently close to the critical temperature
Tc thermal fluctuations are responsible for the experimentally observable
finite resistance. Quite recently it became possible to fabricate sub-10 nm
superconducting structures, where the finite resistivity was reported within
the whole range of experimentally obtainable temperatures. The observation has
been associated with quantum fluctuations capable to quench zero resistivity in
superconducting nanowires even at temperatures T-->0. Here we demonstrate that
in tiny superconducting nanorings the same phenomenon is responsible for
suppression of another basic attribute of superconductivity - persistent
currents - dramatically affecting their magnitude, the period and the shape of
the current-phase relation. The effect is of fundamental importance
demonstrating the impact of quantum fluctuations on the ground state of a
macroscopically coherent system, and should be taken into consideration in
various nanoelectronic applications.Comment: 20 pages, 4 figure
Imprinting superconducting vortex footsteps in a magnetic layer
Local polarization of a magnetic layer, a well-known method for storing information, has found its place in numerous applications such as the popular magnetic drawing board toy or the widespread credit cards and computer hard drives. Here we experimentally show that a similar principle can be applied for imprinting the trajectory of quantum units of flux (vortices), travelling in a superconducting film (Nb), into a soft magnetic layer of permalloy (Py). In full analogy with the magnetic drawing board, vortices act as tiny magnetic scribers leaving a wake of polarized magnetic media in the Py board. The mutual interaction between superconducting vortices and ferromagnetic domains has been investigated by the magneto-optical imaging technique. For thick Py layers, the stripe magnetic domain pattern guides both the smooth magnetic flux penetration as well as the abrupt vortex avalanches in the Nb film. It is however in thin Py layers without stripe domains where superconducting vortices leave the clearest imprints of locally polarized magnetic moment along their paths. In all cases, we observe that the flux is delayed at the border of the magnetic layer. Our findings open the quest for optimizing magnetic recording of superconducting vortex trajectories