Abstract
We have studied the electrical transport properties of ultrathin (4-nm thick) and thick (300-nm thick) films of amorphous (a-)Mo x Si1-x near the zero-field and field- driven superconductor-(metal)-insulator transitions. For thin superconducting films we have observed an anomalous negative magnetoresistance (MR) suggesting the presence of the localized Cooper pairs at T → 0 in perpendicular fields B higher than the critical field B C , while for thick films the negative MR is not visible. These results indicate that the two dimensionality (2D) plays an important role in the appearance of the negative MR (or localized Copper pairs). We have also found from preliminary measurements that the negative MR is no longer visible as the field B ║ is applied parallel to the film surface. This result may suggest the presence of mobile vortices as well as localized Cooper pairs B > B C, consistent with the view of the 2D quantum phase transition.
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Okuma, S., Shinozaki, S., Morita, M. (2000). Magnetoresistance and Vortex States near the Superconductor-Insulator Transition in a-Mo x Si1-x Films. In: Yamashita, T., Tanabe, Ki. (eds) Advances in Superconductivity XII. Springer, Tokyo. https://doi.org/10.1007/978-4-431-66877-0_118
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DOI: https://doi.org/10.1007/978-4-431-66877-0_118
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