PhD project: Composition tuning with solid state electro-transport to look for new states in superconductors.

Project description

A new apparatus for SSE (solid state electrotransport) that we have developed will be used to  finely adjust the stoichiometry of crystals to better approach ideal stoichiometry, increasing the electron mean free path. Unconventional superconductivity is extremely sensitive to electron mean free path and is completely destroyed for low values. The observation of quantum oscillations also require very high mean-free-path samples. Such measurement can be used to map the  Fermi surface, one of the key inputs needed to understand microscopic properties.  The work will focus on improving the quality of materials currently under study in the group, where  preliminary trials indicate SSE could make dramatic improvements. The project would start with a material in which superconductivity co-exists with a charge density wave  (CDW). The charge density wave is suppressed by applying a  modest pressure  at a quantum critical point that is linked to an enhancement of superconducting transition temperature.  This material has potential to form a novel modulated superconducting state (Larkin-Ovvchinikov-Fulde-Ferrel state) at high magnetic field in cleaner samples.  Such a state is modulated along the field direction and expected to be extremely sensitive to the mean free path.  This PhD project would use in-house low temperature facilities to look for evidence of this state and central facilities to explore quantum oscillations  at very high magnetic field to better understand the origin of the CDW and how it interacts with superconductivity.

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