Superconducting Nano-Structures and Devices

 

A superconductor is a material which, when cooled below a certain temperature, loses all resistance to electricity. This means that superconducting materials can carry large electrical currents without any energy loss- but there are limits to how much current can flow before superconductivity is destroyed. The current at which superconductivity breaks down is called the critical current Jc. The value of the maximum possible, or critical current density Jc in superconducting materials is determined by the balance between Lorentz and pinning forces acting on flux lines (FL). Lorentz forces, which act on the current flowing in a vortex, drive FL into motion, which dissipates energy and destroys the perfect conductivity of the superconducting state (Fig.1).

  • Fig.1. The value of the critical current in superconducting materials is determined by the balance of Lorenz forces and pinning forces acting on the flux lines. Lorenz forces which are proportional to the current flow tend to drive the flux lines into motion, which dissipates energy and destroys zero resistance
  • Isolated defects act as local zones of reduced superconducting condensation energy. These sites attract ("pin") FL and oppose their motion and thereby increase Jc. The insertion of many kinds of artificial pinning centers (APC) into practical superconducting materials has been proposed to increase their current carrying capacity, ranging from non-superconducting inclusions (second phases) to proton, neutron or heavy-ion damage tracks inserted via irradiation in accelerator beams. In all of these methods, the APC are randomly distributed over the superconducting material, causing them to operate well below their maximum efficiency. This drawback can be avoided by using special techniques to create a periodic lattice of nano-holes (see Fig.2) so that each pin interacts strongly with at least one, or even a few FL. The introduction of periodic arrays of APC into superconducting samples has been shown to increase the crical current densities by more than 2 orders of magnitude and give rise to novel FL behavior that is not observed in the presence of pinning due to random growth defects or radiation damage.

  • Fig.2. SEM image of nanostructured superconducting device. Nano-patterning leads to the effective pinning of flux lines and the critical current enhancement by more than 100 times in comparison with un-patterned superconductor.
  • After V. Metlushko et al. Phys.Rev.B 59, 603 (1999)

  • From technological point of view, it has become possible to create superconductor quantum devices using nanotechnology, which was previously thought to be practically impossible, and the connection with superconducting quantum computers makes this an important and innovative even further. (V.V. Metlushko, M. Baert, R.Jonckheere, V.V. Moshchalkov, and Y. Bruynseraede, Solid State Communications 91 (1994) 331-335, M. Baert, V.V. Metlushko, R.Jonckheere, V.V. Moshchalkov, and Y.Bruynseraede, Physical Review Letters, 74 (1995) 3269- ISI Citation Classic Award, June 21, 2000 (more than 300 citations)).
    This discovery is now a foundation of Joint European Science Foundation (ESF) Vortex Programme and JSPS Core-to-Core Integrated Action Initiative "Nanoscience and Engineering in Superconductivity" in Japan. Prof. Metlushko was Invited Speaker at all major ESF-JSP Conferences: Combined ESF Vortex and ESF PiShift Workshop, Bad Munstereifel, Germany, 2004, Joint meeting of JSPS Core-to-Core Integrated Action Initiative "Nanoscience and Engineering in Superconductivity" (CTC-NES) and The 4th International Symposium on Intrinsic Josephson Effect and Plasma Oscillations in High-Tc Superconductors (PLASMA 2004), Tsukuba, Japan, November 26-28, 2004, Joint JSPS and ESF Conference on Vortex Matter in Nanostructured Superconductors, (VORTEX IV), Crete, Greece, September 3-9, 2005, the Nanoscale Superconductivity and Magnetism - NSM2006, Satellite M2S-HTSC-VIII Conference, Vaalbeek, Belgium, July 6-8, 2006, Joint ESF and JSPS Conference on Vortex Matter in Nanostructured Superconductors (VORTEX V), 8-14 September 2007, Rhodes, Greece, Sixth International Conference on Vortex Matter in Nanostructured Superconductors (VORTEX VI), 17-24 September 2009, Rhodes, Greece .



    This work was done in collaboration with:

  • G. Crabtree, U. Welp, A. Hoffmann, Materials Science Division, Argonne National Laboratory
  • B.Ilic, Cornell University
  • S.R.J.Brueck, University of New Mexico
  • A. Zhukov, University of Southampton, UK
  • L. DeLong, University of Kentucky
  • S. Field, Colorado State University
  • M. Roseman, P. Grutter, McGill University, Canada
  • V.V. Moshchalkov,Y. Bruynseraede, K.U. Leuven, Belgium



  • Quick Access to Several of Our Recent Publications

  • Direct observation of superconducting vortex clusters pinned by a periodic array of magnetic dots in ferromagnetic/superconducting hybrid structures, PHYSICAL REVIEW B 81, 092505, 2010
  • Self-organized mode-locking effect in superconductor/ferromagnet hybrids, PHYSICAL REVIEW B 79, 054527, 2009
  • Magnetically controlled superconducting weak links, APPLIED PHYSICS LETTERS 95, 032501, 2009
  • Direct visualization of magnetic vortex pinning in superconductors, PHYSICAL REVIEW B 79, 144501,2009
  • Enhanced pinning of superconducting vortices by magnetic vortices, PHYSICAL REVIEW B 77, 060506-R (RAPID COMMUNICATIONS) 2008
  • Switchable magnetic dipole induced guided vortex motion, APPLIED PHYSICS LETTERS 93, 022507, 2008
  • Manipulation of the vortex motion in nanostructured ferromagnetic/superconductor hybrids, APPLIED PHYSICS LETTERS 90, 182501, 2007