The nature of symmetry breaking in the superfluid phase transition in two dimensions is studied. It is shown that, like superfluidity in three dimensions, the superfluid phase transition in two dimensions is characterized by the breaking of a U(1) gauge symmetry. The phase transition does not so much resemble the superfluid phase transition in three dimensions, however, as it does Bogolubov’s η-ensemble theory of the condensation of an ideal Bose gas.
Symmetry-breaking Fermi surface deformations from central interactions in two dimensions