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TT: Fachverband Tiefe Temperaturen

TT 16: Poster Session Superconductivity, Cryogenic Particle Detectors, Cryotechnique

TT 16.7: Poster

Montag, 16. März 2020, 15:00–19:00, P2/EG

Universal behavior of the IMS domain formation in superconducting niobium: Neutron scattering and molecular dynamics simulations — •Abdel Al-Falou^1,2, Alexander Backs^1,2, Michael Schulz^1,2, Alexei Vagov³, Peter Böni², and Sebastian Mühlbauer² — ¹Heinz Maier-Leibnitz Zentrum (MLZ), Garching, Germany — ²Technische Universität München, Garching, Germany — ³Physikalisches Institut, Universität Bayreuth, Germany

In the intermediate mixed state (IMS) of type-II/1 superconductors, vortex lattice and Meissner state domains coexist due to a partial vortex attraction. Recently, we performed a systematic study on the domain formation in the IMS for Nb samples of varying purity [1,2]. Due to the wide range of length scales in the IMS, we combined several neutron based techniques with bulk magnetization measurements. We find a preferred vortex spacing a_VL in the IMS, independent of the external magnetic field. The temperature dependence of a_VL shows a universal behavior, related to the superconducting penetration depth and the sample purity. An elusive key feature so far is the domain morphology in bulk samples. Hence, we use molecular dynamics simulations on a 2D system of vortices as a complementary method, where the vortex interaction is given by extended Ginzburg-Landau theory [3]. In the simulations, we follow a field cooling path analogous to our experiments. The resulting morphology of the IMS depends on several parameters, e.g. the cooling rate or pinning strength. The results can be directly compared to neutron scattering data by Fourier transformation.