Superconductivity with half quantum vortices and two channel Kondo physics

26 April 2019, 2.00 PM - 26 April 2019, 3.00 PM

Andrew Huxley


Half quantum vortices, known to exist in superfluid 3He, harbour localised Majorana states and offer a potential route for constructing a topological quantum computer. If similar vortices could be made in superconductors this would provide a more practical route to achieve this end. My talk will describe what is required to obtain half quantum vortices and identify material parameters that might favour the special type of superconductivity needed to host them. I will then focus on a particular candidate material. At ambient conditions we have found that this material, rather than being a superconductor has an interesting magnetic order on a triangular lattice, while simultaneous displaying quantum critical behaviour at low temperatures. Both states persist in magnetic field. The novel quantum critical behaviour will be interpreted in terms of the combination of two-channel Kondo physics and incommensurate magnetic order and is of interest in its own right. The magnetic order is suppressed with pressure. Finally, I will show very recent results indicating that the material becomes superconducting under pressure. The superconductivity has large critical fields, exceeding the Pauli paramagnetic limit with an anisotropy compatible with the special type of superconductivity sought.

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