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报告人 |
Prof. Victor V. Moshchalkov
Director of INPAC-Institute for Nanoscale Physics and Chemistry,
Department of Physics and Astronomy,
Katholieke University of Leuven, Belgium |
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报告摘要 |
An overview is given of the recent discoveries in the field of the vortex control and manipulation in nanostructured superconductors and superconductor/ferromagnet hybrids, including such new phenomena as the formation of the symmetry-induced antivortices, nanoengineered field-induced superconductivity, multiquanta vortices, vortex ratchets, etc.
In the second part of the talk the existence of the novel superconducting state has been demonstrated in two-component high quality MgB2 single crystalline superconductors where a unique combination of both type-1 and type-2 conditions is realized in a single material: λ1/ξ1<1/√2 for the first component of the order parameter and λ2/ξ2>1/√2 for the second one. Such materials are, in fact, "type-1.5 superconductors" (PRL 102, 117001 (2009); PRB 81, 020506(R) (2010)), since they combine simultaneously both type-1 and type-2 superconductivity. This leads to a drastic change in the vortex-vortex interaction, which results in the appearance of stable vortex stripes, clusters and gossamer-like vortex patterns. We have directly visualized these novel patterns by using Bitter decoration and scanning SQUID microscopy. The observed patterns are in a good agreement with the molecular dynamics simulations based on the vortex-vortex interaction corresponding to the type-1.5 superconductivity. The latter is also compared with the exotic vortex-vortex interactions appearing in single gap superconductors in the vicinity of the special point λ/ξ=1/√2.
*In collaboration with: A.V. Silhanek, M. Menghini, T. Nishio, Q.H. Chen, W. Gillijns, J. Van de Vondel, B. Raes, L.J. Li, J. Guttierez, A. Gebremedhin, B.Y. Zhu, V. H. Dao, L.F. Chibotaru, J. Vanacken, N. D. Zhigadlo, and J. Karpinski
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