TKM Institutsseminar |
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Vortragender: | Roland Willa |
Datum: | 12.12.2017 09:45 |
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Ort: | Room 10.01, 10th Floor, Bldg. 30.23, KIT Campus South |
Zugehörigkeit: | Materials Science Division, Argonne National Laboratory, Lemont IL (USA) |
Gastgeber: | Prof. Dr. Jörg Schmalian |
Abstract
To make superconductors technologically relevant, it is crucial to immobilize flux lines (vortices) threading the material. Capturing the pinning mechanism starting from microscopic interactions of vortices with defects poses a very difficult problem. The theory of strong vortex pinning provides a starting point to address this problem. We revisit the different regimes of strong-pinning theory and investigate them using large-scale numerical solutions of the time-dependent Ginzburg-Landau equations [1]. We explore the magnetic-field dependences of the critical current, jc(B), for superconductors containing spherical inclusions with different sizes and densities. Within a wide range of parameters, the vortex configuration is disordered and features a power-law decay of the critical current, where the power index decreases with the particle density. We find a first-order transition of the pinning ground state towards double-occupancy of defects leading to a non-monotonic pin-breaking force and peak effect. Our results provide a framework for interpretation of pinning properties of real materials and call for further generalization of theory.
[1] R. Willa et al., Supercond. Sci. Tech. 31 014001 (2018)