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 the 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 wave packets, reducing the total condensate density. Depending on the spin-orbit-coupling strength, interatomic attraction, and 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.
Highlights
Understanding Bose-Einstein condensates (BEC) of interacting particles is one of the most interesting problems in condensed matter physics [1]
The spin-orbit coupling (SOC) can be produced in various forms, simulating the Rashba and the Dresselhaus symmetries [14,15] known in solid state physics
The SOC plays a crucial role in BEC physics in uniform three-dimensional gases with interparticle repulsion and makes condensation possible only at zero temperature [30], while at a finite temperature the thermal depletion of the condensate diverges [31]
Summary
Understanding Bose-Einstein condensates (BEC) of interacting particles is one of the most interesting problems in condensed matter physics [1]. The SOC can be produced in various forms, simulating the Rashba and the Dresselhaus symmetries [14,15] known in solid state physics This coupling opens a venue to the appearance of new phases in a variety of ultracold bosonic [16,17,18,19,20,21,22,23,24,25] and fermionic [26,27,28,29] ensembles. The SOC plays a crucial role in BEC physics in uniform three-dimensional gases with interparticle repulsion and makes condensation possible only at zero temperature [30], while at a finite temperature the thermal depletion of the condensate diverges [31].
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