Entangled Superfluids

TL;DR

This paper investigates the dynamics and excitations of entangled Bose-Einstein condensates in a two-species pseudospin-1/2 atomic mixture, revealing multiple superfluid components and their collective excitations.

Contribution

It introduces a detailed analysis of the condensate dynamics and elementary excitations in entangled BECs, including exact solutions for Bogoliubov modes and symmetry considerations.

Findings

Identification of four interdependent superfluid components.

Discovery of three gapless and one gapped Bogoliubov modes.

Analysis of symmetry breaking origins of excitations.

Abstract

We study the condensate dynamics of the so-called entangled Bose-Einstein condensation (EBEC), which is the ground state of a mixture of two species of pseudospin-$\frac{1}{2}$ atoms with interspecies spin-exchange scattering in certain parameter regimes. EBEC leads to four inter-dependent superfluid components, each corresponding to the orbital wave function associated with a spin component of a species. The four superflows have various counter-relations, and altogether lead to a conserved total supercurrent and a conserved total spin supercurrent. In the homogenous case, we also obtain the elementary excitations due to variations of the single-particle orbital wave functions, by exactly solving the generalized time-dependent Bogoliubov equations. There are three gapless Bogoliubov modes and one Klein-Gordon-like gapped mode. The origin of these excitations are also discussed from the perspective of spontaneous breaking of the symmetries possessed by the system.