Dipolar quantum gases, droplets and supersolids

5 problems

• Controlled theory of quantum fluctuations in dipolar droplets

  Open

  Droplets are held together by quantum fluctuations, described by an approximate correction (Lee-Huang-Yang term). Its predictions miss experimental numbers by sizable amounts.

• Lattice supersolid of magnetic atoms in the dipolar Bose-Hubbard model

  Open

  Magnetic atoms in an optical lattice have formed checkerboard and stripe crystals that do not flow. Theory predicts that adding or removing a few atoms should give a lattice supersolid that is both ordered and superfluid.

• Do condensates of polar molecules form supersolids?

  Open

  Molecules with electric dipoles interact far more strongly than magnetic atoms and were recently condensed. Whether they can form a supersolid, and in which range of control fields, is open.

• Finite-temperature phase diagram of a two-dimensional supersolid

  Open

  In two dimensions, heat destroys perfect crystal and superfluid order, leaving only slowly decaying versions. How these two partial orders melt, together or one after another, is unknown.

• Superfluid fraction tensor of a two-dimensional dipolar supersolid

  Partially resolved

  In a supersolid only part of the matter flows freely (the superfluid fraction). It has been measured in a chain of droplets, but not in a two-dimensional crystal where it can depend on direction.