Roton immiscibility in a two-component dipolar Bose gas

TL;DR

This paper investigates the transition between immiscible and miscible phases in a two-component dipolar Bose-Einstein condensate, revealing a novel roton-like transition at finite wave numbers using theoretical and numerical methods.

Contribution

It identifies a new roton-like immiscibility transition in a two-component dipolar BEC within a quasi-two-dimensional setup, combining Bogoliubov analysis and numerical simulations.

Findings

Existence of a roton-like immiscibility transition at finite wave number.

Confirmation of the transition through numerical simulations of coupled Gross-Pitaevskii equations.

Identification of both long-wavelength and roton-like IMTs in dipolar BECs.

Abstract

We characterize the immiscibility-miscibility transition (IMT) of a two-component Bose-Einstein condensate (BEC) with dipole-dipole interactions. In particular, we consider the quasi-two dimensional geometry, where a strong trapping potential admits only zero-point motion in the trap direction, while the atoms are more free to move in the transverse directions. We employ the Bogoliubov treatment of the two-component system to identify both the well-known long-wavelength IMT in addition to a roton-like IMT, where the transition occurs at finite-wave number and is reminiscent of the roton softening in the single component dipolar BEC. Additionally, we verify the existence of the roton IMT in the fully trapped, finite systems by direct numerical simulation of the two-component coupled non-local Gross-Pitaevskii equations.