Two-superfluid Model of Two-component Bose-Einstein Condensates; First Sound and Second Sound

TL;DR

This paper develops a two-superfluid model for two-component Bose-Einstein condensates, drawing parallels to superfluid helium, and explores the behavior of two sound modes analogous to first and second sounds.

Contribution

It formulates a two-superfluid model for two-component BECs based on coupled Gross-Pitaevskii equations, aligning with the superfluid helium two-fluid model.

Findings

The model accurately describes two sound modes in two-component BECs.

Under specific conditions, these sound modes resemble first and second sounds.

The model bridges BEC physics with superfluid helium phenomenology.

Abstract

Superfluid $^4$He at a finite temperature is described by the two-fluid model with the normal fluid component and the superfluid component.We formulate the two-fluid model for two-component BECs, namely two-superfluid model, starting from the coupled Gross-Pitaevskii equations.The two-superfluid model well corresponds to the two-fluid model in superfluid $^4$He.In a special condition, the two sound modes in the two-superfluid model behave like first and second sounds in the two-fluid model of superfluid $^4$He.