Dilute vortices on the surface of superconducting Bi2Sr2CaCu2O8+δ
Abstract
Properties of dilute pancake vortices on the surface of Bi2Sr2CaCu2O8+δ superconductors are investigated by measuring the field, temperature, and time dependencies of the critical current of the surface intrinsic Josephson junctions. It is found that the pinning of the surface vortices has two crossovers over the entire temperature range in the superconducting state. For temperatures below and above ∼20K , strong collective pinning and weaker point defect pinning are observed, respectively. Further increasing the temperature leads to the depinning of the surface vortices. We find that the depinning of the surface vortices can occur at a much lower temperature than that for the bulk vortices, depending on the surface-layer crystalline perfectness or the density of point defects that have been intentionally introduced experimentally.
- Publication:
-
Physical Review B
- Pub Date:
- December 2006
- DOI:
- 10.1103/PhysRevB.74.224508
- Bibcode:
- 2006PhRvB..74v4508W
- Keywords:
-
- 74.25.Qt;
- 74.50.+r;
- 74.72.Hs;
- Vortex lattices flux pinning flux creep;
- Tunneling phenomena;
- point contacts weak links Josephson effects;
- Bi-based cuprates