Harvard Condensed Matter Theory Seminars
Nikolay Prokofiev, University of Massachusetts
- Superfluid disorder in quantum solids
- I will briefly review old ideas on how can superfluidity occur
in a crystalline solid, and discuss a theorem that any supersolid
in continuous space must be in the incommensurate state and have
gapless vacancies and/or interstitials. In He-4 vacanices and
interstitials are gapped, and thus ideal crystals are insulating.
I will present path-integral Monte Carlo data to prove that.
To explain recent experiments on the non-classical moment of
inertia of He-4 solids one has to consider various types of
disorder. I will show examples of superfluid defects in lattice
and helium systems, and discuss which of them are likely to be present
in experimental samples. Finally, I will discuss the "ultimate"
superfluid disordered state---a helium superglass which we observed to
be remarkably stable at low temperatures and elevated pressures.
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