Observation of a new superfluid phase for <sup>3</sup>He embedded in nematically ordered aerogel.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 27669660.
- Also identified by DOI 10.1038/ncomms12975 and PMC identifier 5052659.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
In bulk superfluid <sup>3</sup>He at zero magnetic field, two phases emerge with the B-phase stable everywhere except at high pressures and temperatures, where the A-phase is favoured. Aerogels with nanostructure smaller than the superfluid coherence length are the only means to introduce disorder into the superfluid. Here we use a torsion pendulum to study <sup>3</sup>He confined in an extremely anisotropic, nematically ordered aerogel consisting of ∼10 nm-thick alumina strands, spaced by ∼100 nm, and aligned parallel to the pendulum axis. Kinks in the development of the superfluid fraction (at various pressures) as the temperature is varied correspond to phase transitions. Two such transitions are seen in the superfluid state, and we identify the superfluid phase closest to T<sub>c</sub> at low pressure as the polar state, a phase that is not seen in bulk <sup>3</sup>He.