PhD project: Weighing the Superconducting Condensate

Project description

In a superconductor, measuring the density of Cooper pairs and how this varies with temperature gives precise information on the structure of the energy gap and the symmetry of the order parameter. The standard quantity measured is the penetration depth, which is proportional to the density of Cooper pairs divided by their effective mass. Close to a quantum critical point the mass however has a strong temperature dependence which is of great interest for understanding quantum criticality. The project will develop a little known contact-less method of measurement that will determine the Cooper pair density independently of the effective mass and apply this to investigate materials where quantum criticality drives superconductivity to understand how the change of mass relates to the superconductivity. This research will be done in parallel with thermopower and thermal conductivity measurements. The former are a sensitive probe of topoloogcial changes of the Fermi-surface which may underlie superconductivity in ferromagagnets (see the recent article Yelland et al.). The project can be based in either Edinburgh or in our quantum ordering lab in St Andrews.

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