Hydrodynamics of multi-component Bosonic systems

TL;DR

This paper derives superfluid hydrodynamic equations for multi-component Bose gases at zero temperature, highlighting the role of quantum pressure and extending the framework to systems with long-range interactions, with implications for excitation spectra.

Contribution

It presents a novel derivation of hydrodynamic equations for multi-component Bose gases, including quantum pressure effects and extensions to long-range interactions.

Findings

Quantum pressure is present in nonuniform systems.

Excitation spectrum includes degenerate modes apart from density phonons.

Framework applicable to systems with dipole-dipole interactions.

Abstract

We obtain the superfluid hydrodynamic equations of a multi-component Bose gas with short-ranged interactions at zero temperature under the local equilibrium assumption and show that the quantum pressure is generally present in the nonuniform case. Our approach can be extended to systems with long-range interactions such as dipole-dipole interactions by treating the Hartree energy properly. For a highly symmetric superfluid, we obtain the excitation spectrum and show that except for the density phonon, all other excitations are all degenerate.The implication of our results is discussed.