title: Entropy- and flow-induced superfluid states.
abstract: Normally the role of phase fluctuations in superfluids and superconductors is to drive a phase transition to the normal state. This happens due to proliferation of topologically nontrivial phase fluctuations in the form of vortices. Here we discuss a class of systems where, by contrast, nontopological phase fluctuations can produce superfluidity. Here we understand superfluidity as a phenomenon that does not necessarily arises from a broken U(1) symmetry, but can be associated with a certain class of (approximate or exact) degeneracies of the system's energy landscape giving raise to a U(1)-like phase.
authors.affiliation: Department of Theoretical Physics, The Royal Institute of Technology, Stockholm SE-10691, Sweden.
authors.forename: Johan
authors.initials: J
authors.lastname: Carlström
authors.affiliation: Department of Theoretical Physics, The Royal Institute of Technology, Stockholm SE-10691, Sweden and Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003, USA.
authors.forename: Egor
authors.initials: E
authors.lastname: Babaev