Stability of a flattened dipolar binary condensate: emergence of the spin roton

TL;DR

This paper develops a theoretical framework for a two-component dipolar condensate in a planar trap, identifying regimes where density and spin rotons emerge, and revealing a novel roton-immiscibility transition driven by spin roton softening.

Contribution

It introduces a combined numerical and variational approach to analyze excitation spectra and stability, highlighting the conditions for spin and density rotons and a new roton-immiscibility transition.

Findings

Identification of regimes with density and spin rotons.

Mapping of the stability phase diagram.

Discovery of a roton-immiscibility transition.

Abstract

We develop theory for a two-component miscible dipolar condensate in a planar trap. Using numerical solutions and a variational theory we solve for the excitation spectrum and identify regimes where density- and spin-roton excitations are favored. We characterize the various instabilities that can emerge in this system over a wide parameter regime and present results for the stability phase diagram. Importantly this allows us to identify the parameter regimes where a novel roton-immiscibility transition can occur, driven by the softening of the spin roton excitation.