Introduction to Nonlinear Phenomena in Superfluid Liquids and Bose-Einstein Condensates: Helium, Semiconductors and Graphene

TL;DR

This paper reviews the nonlinear dynamics of superfluid liquids and Bose-Einstein condensates, emphasizing Hamiltonian hydrodynamics and the effects of energy pumping on out-of-equilibrium quantum systems like helium and graphene-based condensates.

Contribution

It introduces a Hamiltonian approach to nonlinear phenomena in superfluid and BEC systems, analyzing out-of-equilibrium dynamics under energy pumping in various quantum fluids.

Findings

Nonlinear coupling significantly influences system dynamics.

Out-of-equilibrium superfluid helium exhibits unique properties.

Exciton polariton condensates in semiconductors and graphene are affected by high magnetic fields.

Abstract

We review current understanding of the non-equilibrium dynamics of collective quantum systems. We describe an approach based on the Hamiltonian formulation of superfluid hydrodynamics. It is shown that, in the presence of constant energy pumping, the nonlinear coupling of fluctuations in the density and entropy strongly affects the nonequilibrium dynamics of the system. We use the results obtained to analyze the properties of out-of-equilibrium superfluid 4He and of exciton polariton Bose-Einstein condensates, both in semiconductor quantum wells and in graphene layers in presence of high magnetic field.