Surprises in superfluids

Charles Day

A one-dimensional Bose-Einstein condensate's superfluid state is surprisingly robust if the atoms are trapped in a quasiperiodic lattice. By Charles Day ABose-Einstein condensate of cold atoms occupying a periodic lattice can flow like a superfluid.But if the atoms' mutual repulsion is strengthened and the lattice potential deepened, the atoms can become immobilized in a state known as a Mott insulator.Now Hepeng Yao of the University of Geneva and his collaborators have examined the Mott transition of cold atoms trapped in a lattice that is quasiperiodic rather than periodic [1].Given that quasiperiodicity and other kinds of disorder tend to trap particles, the researchers were surprised to discover that their quasiperiodic lattice sustained the superfluid state rather than weakening it.

A Correspondent

Kurt Alfred Georg Mendelssohn

Jelena Stajic

Helium Superfluidity When physicists rotate the superfluid 4He, it develops a regular array of tiny whirlpools, called vortices. The same phenomenon should occur in helium droplets half a micrometer in size, but studying individual droplets is tricky. Gomez et al. used x-ray diffraction to deduce the shape of individual rotating droplets and image the resulting vortex patterns, which confirmed the superfluidity of the droplets. They found that superfluid droplets can host a surprising number of vortices and can rotate faster than normal droplets without disintegrating. Science , this issue p. [906][1] [1]: /lookup/doi/10.1126/science.1252395

Zaira Nazario, B. W. A. Leurs, David Santiago +1 more

Exploiting analogies between spin-orbit coupled spin superfluids and non-Abelian Yang-Mills theory, we argue that machines can be built capable of trapping a quantized amount of electric linear charge density, while the line charge quantum itself is surprisingly large. The required conditions might well hold in superfluid 3He-B, for which we propose an experimental realization of this phenomenon.

K.H. Bennemann, John B. Ketterson