Exotic Phenomena in Superfluid 3He at Ultralow Temperatures

Lead Research Organisation: Lancaster University
Department Name: Physics

Abstract

Superfluid 3He is the most exotic liquid in existence. It only exists below a few thousandths of a degree above absolute zero. It owes its existence entirely to quantum mechanics and is therefore interesting to study to promote the better understanding of quantum systems in general. While it is superfluid and may flow without friction, the fact that it also has an associated spin 'superfluid' and an orbital angular momentum 'superfluid' gives it many unique properties, many of which remain to be discovered. Our group has pioneered the study of ballistic heat transport in superfluid 3He. Heat in the superfluid is carried by quasiparticle excitations. At very low temperatures these are so few as to hardly ever scatter. We can thus generate beams of ballistic quasiparticles and fire them at various obstacles formed by the superfluid itself. We have so far mastered the techniques for observing the Andreev reflection of such beams (a form of reflection unique to superfluids and superconductors). We now wish to develop the methods needed to measure the transmission of quasiparticle beams.We will use this technique to investigate the decay of quantum turbulence. In superfluid 3He turbulence takes the form of a tangle of identical quantised vortex lines. This is much simpler than classical turbulence which has eddies/vortices of variable sizes. The study of superfluid turbulence will give us a better understanding of turbulence in general. With quasiparticle transmission techniques we hope to obtain more quantitative information on the turbulence decay mechanisms in the zero-temperature limit where the dissipation mechanism should be determined by quantum effects rather than by conventional viscosity. We will also investigate the superfluid phase diagram of dirty 3He. Impurities may be effectively added to liquid 3He by confining it in aerogel, a nanoscale network of silica strands. Since pure 3He is so well understood, it is the ideal substance for investigating such effects. We will study how impurities influence the various superfluid phases and the transitions between them. Gapless superfluidity is an exotic phenomenon common in dirty superconductors where the binding energy of the constituent pairs providing the superfluid behaviour vanishes. We have recently seen this behaviour in the thermal conductivity of superfluid. With similar techniques we plan to study the cross-over from gapless to (the usual) gapped superfluidity. Further, where the superfluid transition in aerogel occurs at zero temperature, this constitutes a quantum phase transition dominated by quantum effects. This seems to be the cleanest such transition known and we are well placed to investigate the associated quantum fluctuations.The superfluid orbital properties of 3He are not evident at the temperatures available to most research groups. Our novel techniques allow us the lowest achievable temperatures where orbital superfluidity becomes apparent. We have indirect evidence of orbital superfluidity from exotic NMR signals from persistent precessing domains (PPDs). These are ultra long lived domains of coherent spin precession which have laser-like properties. By looking at the interaction of two PPDs we hope to gain more direct evidence of orbital superfluidity.Finally we plan to demonstrate an exotic mechanism unique to superfluid 3He affecting the motion of an object in the liquid. At absolute zero there are no excitations and an object should move freely through the superfluid as through a vacuum. However, if the object is heated, the thermal emission of quasiparticles should damp its motion. We will investigate this by moving a heated aerogel sample through the superfluid.We emphasise that most of the proposed experiments are only feasible at the very lowest temperatures made possible by our unique cooling techniques.

Publications

10 25 50
 
Description We have made much progress in understanding how to image turbulence in quantum fluid systems which is much simpler than the classical phenomenon.

We have designed a new imaging spectrometer which has the ability to detect and image the presence and evolution of a tangle of quantum vortices at the very lowest attainable temperatures (~ 100 microkelvin).

A key general finding is that these experiments have demonstrated that we can reach and make experiments in the condensate in the unique temperature region where there are virtually no excitations. This is an exciting new area opening up and we are currently the World leaders in these studies.
Exploitation Route The knowledge gained will help others to be able to work in the 100 microkelvin regime in superfluid 3He where there is a wealth of new phenomena in the "pure condensate" regime waiting to be accessed.
Sectors Aerospace, Defence and Marine,Education,Manufacturing, including Industrial Biotechology,Other

 
Description The work here feeds into UK industry's long-term planning for microkelvin experiments as a large fraction of the Worlds manufacturing in the area is situated in the UK.
First Year Of Impact 2016
Sector Manufacturing, including Industrial Biotechology
Impact Types Economic

 
Description EU FP7 Infrastructure Project MICROKELVIN 2009-2014 
Organisation Aalto University
Department Department of Applied Physics
Country Finland 
Sector Academic/University 
PI Contribution This was an FP7 Infrastructure Network, where Lancaster was one of the three access-giving hubs. Thus we played a senior role in the consortium with GRP acting as chairman of the governing council.
Collaborator Contribution We undertook joint research projects with the other partners and provided experimental access to our facilities (paid for by FP7) for partnmers and others to run experiments at Lancaster.
Impact Many publications already listed under EPSRC grants.
Start Year 2009
 
Description EU FP7 Infrastructure Project MICROKELVIN 2009-2014 
Organisation BlueFors Cryogenics
Country Finland 
Sector Private 
PI Contribution This was an FP7 Infrastructure Network, where Lancaster was one of the three access-giving hubs. Thus we played a senior role in the consortium with GRP acting as chairman of the governing council.
Collaborator Contribution We undertook joint research projects with the other partners and provided experimental access to our facilities (paid for by FP7) for partnmers and others to run experiments at Lancaster.
Impact Many publications already listed under EPSRC grants.
Start Year 2009
 
Description EU FP7 Infrastructure Project MICROKELVIN 2009-2014 
Organisation European Organization for Nuclear Research (CERN)
Department Physics Department
Country Switzerland 
Sector Academic/University 
PI Contribution This was an FP7 Infrastructure Network, where Lancaster was one of the three access-giving hubs. Thus we played a senior role in the consortium with GRP acting as chairman of the governing council.
Collaborator Contribution We undertook joint research projects with the other partners and provided experimental access to our facilities (paid for by FP7) for partnmers and others to run experiments at Lancaster.
Impact Many publications already listed under EPSRC grants.
Start Year 2009
 
Description EU FP7 Infrastructure Project MICROKELVIN 2009-2014 
Organisation Heidelberg University
Department Department of Physics and Astronomy
Country Germany 
Sector Academic/University 
PI Contribution This was an FP7 Infrastructure Network, where Lancaster was one of the three access-giving hubs. Thus we played a senior role in the consortium with GRP acting as chairman of the governing council.
Collaborator Contribution We undertook joint research projects with the other partners and provided experimental access to our facilities (paid for by FP7) for partnmers and others to run experiments at Lancaster.
Impact Many publications already listed under EPSRC grants.
Start Year 2009
 
Description EU FP7 Infrastructure Project MICROKELVIN 2009-2014 
Organisation Leiden University
Department Leiden Institute of Physics
Country Netherlands 
Sector Academic/University 
PI Contribution This was an FP7 Infrastructure Network, where Lancaster was one of the three access-giving hubs. Thus we played a senior role in the consortium with GRP acting as chairman of the governing council.
Collaborator Contribution We undertook joint research projects with the other partners and provided experimental access to our facilities (paid for by FP7) for partnmers and others to run experiments at Lancaster.
Impact Many publications already listed under EPSRC grants.
Start Year 2009
 
Description EU FP7 Infrastructure Project MICROKELVIN 2009-2014 
Organisation NEEL Institute
Country France 
Sector Public 
PI Contribution This was an FP7 Infrastructure Network, where Lancaster was one of the three access-giving hubs. Thus we played a senior role in the consortium with GRP acting as chairman of the governing council.
Collaborator Contribution We undertook joint research projects with the other partners and provided experimental access to our facilities (paid for by FP7) for partnmers and others to run experiments at Lancaster.
Impact Many publications already listed under EPSRC grants.
Start Year 2009
 
Description EU FP7 Infrastructure Project MICROKELVIN 2009-2014 
Organisation Physikalisch-Technische Bundesanstalt
Country Germany 
Sector Public 
PI Contribution This was an FP7 Infrastructure Network, where Lancaster was one of the three access-giving hubs. Thus we played a senior role in the consortium with GRP acting as chairman of the governing council.
Collaborator Contribution We undertook joint research projects with the other partners and provided experimental access to our facilities (paid for by FP7) for partnmers and others to run experiments at Lancaster.
Impact Many publications already listed under EPSRC grants.
Start Year 2009
 
Description EU FP7 Infrastructure Project MICROKELVIN 2009-2014 
Organisation Royal Holloway, University of London
Department Department of Physics
Country United Kingdom 
Sector Academic/University 
PI Contribution This was an FP7 Infrastructure Network, where Lancaster was one of the three access-giving hubs. Thus we played a senior role in the consortium with GRP acting as chairman of the governing council.
Collaborator Contribution We undertook joint research projects with the other partners and provided experimental access to our facilities (paid for by FP7) for partnmers and others to run experiments at Lancaster.
Impact Many publications already listed under EPSRC grants.
Start Year 2009
 
Description EU FP7 Infrastructure Project MICROKELVIN 2009-2014 
Organisation Slovak Academy of Sciences
Department Institute of Experimental Physics SAS
Country Slovakia 
Sector Academic/University 
PI Contribution This was an FP7 Infrastructure Network, where Lancaster was one of the three access-giving hubs. Thus we played a senior role in the consortium with GRP acting as chairman of the governing council.
Collaborator Contribution We undertook joint research projects with the other partners and provided experimental access to our facilities (paid for by FP7) for partnmers and others to run experiments at Lancaster.
Impact Many publications already listed under EPSRC grants.
Start Year 2009
 
Description EU FP7 Infrastructure Project MICROKELVIN 2009-2014 
Organisation University of Ottawa
Department Department of Physics
Country Canada 
Sector Academic/University 
PI Contribution This was an FP7 Infrastructure Network, where Lancaster was one of the three access-giving hubs. Thus we played a senior role in the consortium with GRP acting as chairman of the governing council.
Collaborator Contribution We undertook joint research projects with the other partners and provided experimental access to our facilities (paid for by FP7) for partnmers and others to run experiments at Lancaster.
Impact Many publications already listed under EPSRC grants.
Start Year 2009