Dynamical and energetic instabilities in multi-component Bose-Einstein condensates in optical lattices

TL;DR

This paper analyzes the stability of multi-component Bose-Einstein condensates in optical lattices, deriving criteria for dynamical and energetic instabilities and exploring how interactions and external fields influence superfluid flow stability.

Contribution

It provides analytical stability criteria for multi-component BECs in optical lattices, including two-species and spinor condensates, revealing how interactions and external fields affect stability.

Findings

Presence of one condensate can stabilize the other’s superfluid flow.

Superfluid flow stability can be tuned by superfluid velocities.

Magnetic Zeeman shifts can stabilize superfluid flow in certain cases.

Abstract

We study dynamical and energetic instabilities in the transport properties of Bloch waves for atomic multi-component Bose-Einstein condensates in optical lattices in the tight-binding limit. We obtain stability criteria analytically, as a function of superfluid velocities and interaction parameters, in several cases for two-component and spinor condensates. In the two-species case we find that the presence of the other condensate component can stabilize the superfluid flow of an otherwise unstable condensate and that the free space dynamical miscibility condition of the two species can be reversed by tuning the superfluid flow velocities. In spin-1 condensates, we find the steady-state Bloch wave solutions and characterize their stability criteria. We find generally more regions of dynamical instability arise for the polar than for the ferromagnetic solutions. In the presence of magnetic Zeeman shifts, we find a richer variety of condensate solutions and find that the linear Zeeman shift can stabilize the superfluid flow in several cases of interest.