30 research outputs found
Vortex phase diagram in BSCCO with damage tracks created by 30 MeV fullerene irradiation
Using 30 MeV C60 fullerene irradiation, we have produced latent tracks of
diameter 20 nm and length 200 nm, near the surface of single crystalline BSCCO.
A preliminary transmission electron microscopy study shows evidence for a very
high density of deposited energy, and the ejection of material from the track
core in very thin specimens. The latent tracks reveal themselves to be
exceptionally strong pinning centers for vortices in the superconducting mixed
state. Both the critical current density and magnetic irreversibility line are
significantly enhanced. The irradiated crystals present salient features of the
(B,T) phase diagram of vortex matter both of pristine crystals, such as the
first order vortex phase transition, and the exponential Bose-glass line
characteristic of heavy ion-irradiated crystals. We show that the latter is
manifestly independent of the pinning potential.Comment: 10 pages, 13 figure
Direct evidence of the anisotropic structure of vortices interacting with columnar defects in high-temperature superconductors through the analysis of Lorentz images
Two types of Fresnel contrasts of superconducting vortices in a Lorentz micrograph, corresponding to pinned and unpinned vortices, were obtained by a newly developed 1 MV field-emission transmission electron microscope on a Bi2Sr2CaCu2O8+delta (Bi-2212) thin specimen containing tilted linear columnar defects introduced by heavy ion irradiation. The main features of the Fresnel contrasts could be consistently interpreted by assuming that the vortices are pinned along the tilted Columnar defects and by using a layered or an anisotropic model to calculate the phase shift of the electron wave. The confirmed validity of both models strongly indicates that superconducting vortices in high-critical temperature (high-T-c) layered materials have an anisotropic structure