Condensed Matter Physics Seminar

2 p.m., Thursday, October 24, 2002
Room 1201, Physics Building

 Are Superconductors Really Superconducting in a Magnetic Field?

Chris Lobb


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 superconducting state[1].

[1] 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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