Superfluidlike

Superfluidlike is a descriptive term used in physics to denote systems that exhibit certain features reminiscent of superfluidity but do not fully meet its defining criteria. In the strict sense, a superfluid refers to a phase of matter that flows without viscosity, supports a macroscopic quantum phase, and shows characteristic hydrodynamics at low temperatures. “Superfluidlike” is used when a system shows some of these hallmarks, such as reduced dissipation, coherent flow, or the formation of quantized vortices, while either operating out of equilibrium, at higher temperature, or lacking a true thermodynamic phase with long-range order.

Contexts where the term appears include ultracold atomic gases in traps that exhibit flow patterns and suppressed drag; exciton-polariton condensates in semiconductor microcavities that display coherent flow and vortex behavior despite driven-dissipative conditions; and certain superconducting or strongly correlated materials where frictionless transport is observed under specific conditions but without a conventional Bose-Einstein condensate.

Theoretical descriptions often employ mean-field models such as the Gross-Pitaevskii equation, along with hydrodynamic approaches that treat a complex order parameter. The Landau criterion for critical velocity and the nucleation of quantized vortices are frequently invoked to interpret superfluidlike behavior. The term is especially common in non-equilibrium or finite-size systems where pumping and dissipation complicate a full thermodynamic realization of superfluidity.

Limitations include dissipative processes, finite-size effects, and thermal fluctuations that can prevent a true superfluid state, so the label remains an approximate characterization rather than a definitive phase. It is used to describe systems that share a subset of superfluid properties without claiming exact equivalence. See also: Superfluidity, Bose-Einstein condensation, Exciton-polaritons, Gross-Pitaevskii equation.