Condensed Matter Physics Seminar
2 p.m., Thursday, October 24, 2002
Room 1201, Physics Building
Are Superconductors Really Superconducting in a Magnetic Field?
Abstract: DC voltage versus current measurements of superconductors
in a magnetic field are widely interpreted to imply that a phase transition
occurs into a state of zero resistance. We show that the widely-used scaling
function approach has a problem: Good data collapse occurs for a wide range of
critical exponents and temperatures. This strongly suggests that agreement with
scaling alone does not prove the existence of the phase transition. We discuss a
criterion to determine if the scaling analysis is valid, and find that all of
the data in the literature that we have analyzed fail to meet this criterion.
Our data on YBCO films, and other data that we have analyzed, are more
consistent with the occurrence of small but non-zero resistance at low
temperature, indicating that there is not a phase transition to a
 D. R. Strachan, M. C. Sullivan, P. Fournier, S.
P. Pai, T. Venkatesan, and C. J. Lobb, Do Superconductors Have Zero Resistance
in a Magnetic Field?, Phys. Rev. Lett. 87, 067007-1 through 067007-4 (2001) (arXiv:cond-mat/0011014).
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