Maria Navarro Gastiasoro – Niels Bohr Institute - University of Copenhagen

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Niels Bohr Institute > Research > PhD theses 2016 > 2016 > Maria Navarro Gastiasoro

 

Maria Navarro GastiasoroMaria Navarro Gastiasoro

A thesis submitted  January 2016 for the degree of Doctor of Philosophy and defended May 16, 2016.

The PhD School of Science
Faculty of Science, Niels Bohr Institute, Condensed Matter Physics, University of Copenhagen, Denmark

Academic supervisor: Brian M. Andersen

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Abstract

Emergent disorder phenomena in correlated Fe-based superconductors

The fundamental pairing mechanism causing high-T superconductivity in Febased superconductors remains controversial. Superconductivity is only one of several phases exhibited by these materials, and it is widely believed that the mechanism responsible for pairing may be closely linked to the existence of other proximate ordered phases. Most of these materials are obtained by chemical doping, which besides extra carriers, introduces disorder in the system. Therefore, understanding the role of these impurities is crucial, and is a main focus of our work.

In this thesis, we start with the assumption that the observed electronic phases are captured within the itinerant electron scenario. We investigate competing spin density wave phases in homogeneous systems, but also in disordered systems where the interaction between impurity moments becomes relevant. The theory of emergent states around potentials in multi-band systems is introduced, and we propose strongly anisotropic defect states as a source of the reported transport anisotropy. Finally, we discuss unconventional correlation-driven disorder phenomena in the superconducting state, revealing a highly unusual impurity response.

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