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Details of Grant 

EPSRC Reference: EP/R04533X/1
Title: Topological mesoscopic superfluidity of 3He
Principal Investigator: Saunders, Professor J
Other Investigators:
Rojas, Dr X D Cowan, Professor B Eschrig, Professor M
Casey, Dr AJ Levitin, Dr LV
Researcher Co-Investigators:
Dr P J Heikkinen
Project Partners:
Kyoto University Montana State University Northwestern University
Oxford Instruments Ltd University of Jyvaskyla University of Oxford
York Instruments
Department: Physics
Organisation: Royal Holloway, Univ of London
Scheme: Standard Research
Starts: 01 July 2018 Ends: 31 December 2021 Value (£): 1,406,300
EPSRC Research Topic Classifications:
Condensed Matter Physics
EPSRC Industrial Sector Classifications:
No relevance to Underpinning Sectors
Related Grants:
Panel History:
Panel DatePanel NameOutcome
25 Apr 2018 EPSRC Physical Sciences - April 2018 Announced
Summary on Grant Application Form
Helium remains liquid down to the absolute zero of temperature through a combination of relatively weak interatomic interactions and quantum zero point motion. It provides models for studying systems of strongly interacting bosons (4He) and fermions (3He). These materials have played a key role in the development of concepts central to condensed matter physics: Bose-Einstein condensation; macroscopic quantum physics; topological phase transitions; the Landau Fermi liquid theory of electrons in metals; unconventional superconductivity; topological quantum matter. The richest system is superfluid 3He (recognized in the 1996 and 2003 Nobel Prizes), the conceptual reach of which is described by Volovik in terms of a "3He-centric universe", conceptually linked to most major fields of physics.

Condensed matter systems feature in every modern technology. The development of this technology has relied on the discovery and creation of new materials with new phases and often unanticipated properties, as well as hybrid devices which combine these materials, increasingly on the nanoscale.

Recently the understanding of new phases solely in terms of symmetry breaking has been shown to be inadequate in some cases. This is the notion of topological quantum matter (2016 Nobel Prize). Two important classes of quantum matter are at the centre of attention: topological insulators and topological superconductors. Usual insulators do not conduct electricity, because of an energy gap between filled and empty energy bands. But in a topological insulator the momentum space topology of the band structure necessarily gives rise to conducting surface excitations. On the other hand, as a metal is cooled into its superconducting state, a gap emerges. Topological superconductors also support surface/edge excitations, and there are substantial efforts to identify materials that are bulk topological superconductors.

This project will exploit superfluid 3He, known to support two distinct topological superfluid phases in bulk, establishing the new research direction of topological mesoscopic superfluidity. Under nanoscale confinement, this material provides a unique model for topological superconductivity. The subtle interplay between symmetry and topology in these materials is an open question. Our approach will be to confine 3He in precisely engineered geometries to create hybrid nanostructures, allowing a degree of control that is unprecedented. Confinement and periodic structures, with liquid pressure as a tuning parameter of Cooper pair diameter, will induce new superfluid phases, for which the order parameter symmetry will be inferred from nuclear magnetic resonance. These materials will be building blocks for hybrid mesoscopic superfluid systems.

Excitations emerge at surfaces/edges/interfaces of the topological superfluid. As well as the interface with inert matter, where we can tune surface scattering in situ, stepped confinement in hybrid structures will create intra-fluid interfaces of the highest quality. Surface and edge spin currents in time reversal invariant superfluid 3He-B will be investigated by NMR and their coupling to confined Anderson-Higgs order parameter collective modes, as well as nano-wires of diameter similar to that of Cooper pairs. Our ambition is to detect non-local response of the surface Majorana modes. Edge states in chiral superfluid 3He-A will be investigated by a predicted anomalous Hall effect in mass and thermal transport. Interface states will be investigated by thermal transport.

This project has a strong international collaborative dimension, including partnerships with Cornell, NIST and PTB (Berlin). Partnerships with theorists from the USA, Europe and Japan are central to the design and interpretation of experiments. Partnerships within the scientific instruments industry will deliver short-medium term impact from the technical developments central to this project.

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