Superconducting vortex matter under temporal and spatial perturbations

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Larsen, Camilla Buhl ORCID: https://orcid.org/0000-0002-5775-5258 (2020). Superconducting vortex matter under temporal and spatial perturbations. University of Birmingham. Ph.D.

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Abstract

Understanding the behaviour of the flux line lattice (FLL) of type-II superconductors under external perturbations is crucial for the development of superconducting technologies.

By employing time-resolved small angle neutron scattering (SANS), we investigate the niobium FLL when perturbed by an external AC field. Our dynamic investigation is carried out along a fourfold [100] crystallographic direction, which affects the observed characteristic time constants significantly. We investigate the dynamic behaviour across different structural vortex phase transitions and observe no softening of the lattice close to the transitions. Non-elastic features are also observed.

SANS is also used to investigate an impure vanadium sample. We explore the well-known Bragg glass and the more elusive vortex glass. Measurements of longitudinal correlation lengths indicate that the vortex glass in vanadium is dominated by short-range order correlations. Muon spin rotational measurements show that the skew of the local field distribution becomes negative in the vortex glass phase. The negative skew distributions are further investigated with time-dependent Ginzburg-Landau simulations (TDGL), showing that negative skew can be achieved through positional disorder or vortex core deformations. We illustrate the potential of applying the TDGL simulations in Monte Carlo optimization procedures.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):