PhD project: Unconventional Superconductivity with 1/2 quantum vortices

Project description

Vortices are topologically protected stable structures. In type II superconductors they allow magentic flux to penetrate in multiples of the flux quantum. For a particular type of unconventional superconductor half-quantum vortices are possible. This requires odd-parity superconductivity that has an extra degree of freedom represented by a vector d that is free to rotate (physically the direction of d gives the direction along which the spin of the Cooper pairs in an odd parity superconducting state is zero). Such Vortices would have interesting quantum statistics that may be harnessed to build a quantum computer that is topologically protected from decoherence. The project will work on a new superconductor that potentially displays these states, albeit only under high-pressure.

More information on this material can be found here: https://www.pnas.org/doi/10.1073/pnas.2210235119

We have calculated that there should be a transition as a function of field below which single quantum vortices separate into pairs of half quantum vortices.  The project will develop ultrasound measurements to detect both changes in sound velocity and absorption across the transition.   

The project is primarily experimental but the experimental work can be combined with calculating the expected signatures of the transition to half quantum vortices and modelling the ultrasound measurements.  It will also link to studying unconventional superconductivity and quantum criticality more generally.

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