Collapse of spin-orbit coupled Bose-Einstein condensates

TL;DR

This paper develops a theoretical framework for understanding how spin-orbit coupling influences the collapse of attractive Bose-Einstein condensates, revealing mechanisms that can prevent or modify collapse.

Contribution

It introduces a theory showing how different types of spin-orbit coupling can control collapse in attractive BECs, extending their stability domain.

Findings

Spin-dependent velocity can prevent collapse via centrifugal effects.

Spin-orbit coupling can cause spatial splitting, reducing density.

Collapse can be controlled or suppressed by tuning spin-orbit interactions.

Abstract

A finite-size quasi two-dimensional Bose-Einstein condensate collapses if the attraction between atoms is sufficiently strong. Here we present a theory of collapse for condensates with the interatomic attraction and spin-orbit coupling. We consider two realizations of spin-orbit coupling: the axial Rashba coupling and balanced, effectively one-dimensional, Rashba-Dresselhaus one. In both cases spin-dependent "anomalous" velocity, proportional to the spin-orbit coupling strength, plays a crucial role. For the Rashba coupling, this velocity forms a centrifugal component in the density flux opposite to that arising due to the attraction between particles and prevents the collapse at a sufficiently strong coupling. For the balanced Rashba-Dresselhaus coupling, the spin-dependent velocity can spatially split the initial state in one dimension and form spin-projected wavepackets, reducing the total condensate density. Depending on the spin-orbit coupling strength, interatomic attraction, and the initial state, this splitting either prevents the collapse or modifies the collapse process. These results show that the collapse can be controlled by a spin-orbit coupling, thus, extending the domain of existence of condensates of attracting atoms.