Agenda

Next Quantum Material Seminar/LANEF:

Thursday, May 4th 2023 at 2:00 pm

Andrew Huxley (University of Edinburgh)

“ Extended non-Fermi-Liquid states, unconventional superconductivity and half-quantum vortices”

To access this seminar:

Institut Néel CNRS, Building K, Room Rémy Lemaire  (K223)

Abstract: Half-quantum vortices in a superconductor would provide a possible route for quantum computation that is topologically protected and immune from decoherence. This motivated the search for a material with a superconducting order parameter that could host such vortices.

The material chosen, uranium diauride (UAu2), is not a superconductor at room pressure, but instead is a magnetically ordered metal. The low temperature state is a non-fermi liquid. Non-fermi liquids (NFL) are typically found above quantum critical points where magnetic order is suppressed and are disrupted by magnetic field. The non-fermi-liquid behaviour seen in uranium diauride breaks this paradigm, with the NFL behaviour persisting in field and becoming more marked as the magnetic ordering temperature increases [1,2]. This suggests that UAu2’s NFL behaviour is intrinsic to the magnetic state. The magnetic state is unusual, reflecting the frustration inherent in a stacked triangular lattice. A possible explanation for the NFL behaviour based on this will be given.

The magnetic order and NFL behaviour are suppressed with pressure. At and above the pressure the magnetic order disappears, superconductivity occurs [2]. The critical field exceeds the standard paramagnetic limit suggesting the superconductivity is an equal spin paired state. The critical field also has an unusual anisotropy that could be explained by a two-component superconducting order of the type sought after.

References:

[1] “Non-fermi liquid behaviour below the Neel temperature in the frustrated heavy Fermion magnet UAu2”. Christopher D. O’Neill, Julian L Schmehr, Harry D. J. Keen, Luke Pritchard Cairns, Dmitry A Sokolov, Andreas Hermann, Didier Wermeille, Pascal Manuel, Frank Kruger and Andrew D. Huxley, Proceedings of the National Academy of Sciences of the United States of America, 118, 49 (2021)

[2] “Multicomponent odd-parity superconductivity in UAu2 at high pressure”, Christopher D. O’Neill, Julian L. Schmehr, and Andrew D. Huxley, Proceedings of the National Academy of Sciences of the United States of America, 119, 51 (2022)

The organizers:

Elsa Lhotel (elsa.lhotel@neel.cnrs.fr)
Florence Levy-Bertrand (florence.levy-bertrand@neel.cnrs.fr)