scholarly journals Surface Excitations, Shape Deformation, and the Long-Time Behavior in a Stirred Bose–Einstein Condensate

2018 ◽  
Vol 3 (4) ◽  
pp. 41
Author(s):  
Qing-Li Zhu ◽  
Jin An
Keyword(s):  
Rotation Frequency ◽  
Slow Motion ◽  
Einstein Condensate ◽  
Shape Deformation ◽  
Time Behavior ◽  
Bose Einstein Condensate ◽  
Vortex Dipole ◽  
Long Time ◽  
Beam Center ◽  
Bose Einstein

The surface excitations, shape deformation, and the formation of persistent current for a Gaussian obstacle potential rotating in a highly oblate Bose–Einstein condensate (BEC) are investigated. A vortex dipole can be produced and trapped in the center of the stirrer even for the slow motion of the stirring beam. When the angular velocity of the obstacle is above some critical value, the condensate shape can be deformed remarkably at the corresponding rotation frequency followed by surface wave excitations. After a long enough time, a small number of vortices are found to be either trapped in the condensate or pinned by the obstacle, and a vortex dipole or several vortices can be trapped at the beam center, which provides another way to manipulate the vortex.

scholarly journals Non-equilibrium evolution of Bose-Einstein condensate deformation in temporally controlled weak disorder

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Milan Radonjic ◽  
Axel Pelster
Keyword(s):  
Mean Field ◽  
Einstein Condensate ◽  
Weak Disorder ◽  
Field Approach ◽  
Bose Einstein Condensate ◽  
Adiabatic Switching ◽  
Long Time ◽  
Disorder Potential ◽  
Bose Einstein ◽  
Non Equilibrium

We consider a time-dependent extension of a perturbative mean-field approach to the homogeneous dirty boson problem by considering how switching on and off a weak disorder potential affects the stationary state of an initially {equilibrated} Bose-Einstein condensate by the emergence of a disorder-induced condensate deformation. We find that in the switch on scenario the stationary condensate deformation turns out to be a sum of an equilibrium part{, that actually corresponds to adiabatic switching on the disorder,} and a dynamically-induced part, where the latter depends on the particular driving protocol. If the disorder is switched off afterwards, the resulting condensate deformation acquires an additional dynamically-induced part in the long-time limit, while the equilibrium part vanishes. {We also present an appropriate generalization to inhomogeneous trapped condensates.} Our results demonstrate that the condensate deformation represents an indicator of the generically non-equilibrium nature of steady states of a Bose gas in a temporally controlled weak disorder.

scholarly journals Snell's Law for a vortex dipole in a Bose-Einstein condensate

2019 ◽  
Vol 6 (3) ◽  
Author(s):  
Michael MacCormick Cawte ◽  
Xiaoquan Yu ◽  
Brian P. Anderson ◽  
Ashton Bradley
Keyword(s):  
Total Internal Reflection ◽  
Finite Size ◽  
Einstein Condensate ◽  
Quantum Vortex ◽  
Bose Einstein Condensate ◽  
Vortex Dipole ◽  
Wide Range ◽  
Snell’S Law ◽  
Snell's Law ◽  
Bose Einstein

A quantum vortex dipole, comprised of a closely bound pair of vortices of equal strength with opposite circulation, is a spatially localized travelling excitation of a planar superfluid that carries linear momentum, suggesting a possible analogy with ray optics. We investigate numerically and analytically the motion of a quantum vortex dipole incident upon a step-change in the background superfluid density of an otherwise uniform two-dimensional Bose-Einstein condensate. Due to the conservation of fluid momentum and energy, the incident and refracted angles of the dipole satisfy a relation analogous to Snell’s law, when crossing the interface between regions of different density. The predictions of the analogue Snell’s law relation are confirmed for a wide range of incident angles by systematic numerical simulations of the Gross-Piteavskii equation. Near the critical angle for total internal reflection, we identify a regime of anomalous Snell’s law behaviour where the finite size of the dipole causes transient capture by the interface. Remarkably, despite the extra complexity of the interface interaction, the incoming and outgoing dipole paths obey Snell’s law.

scholarly journals Giant vortex clusters in a two-dimensional quantum fluid

Science ◽  
2019 ◽  
Vol 364 (6447) ◽  
pp. 1264-1267 ◽  
Author(s):  
Guillaume Gauthier ◽  
Matthew T. Reeves ◽  
Xiaoquan Yu ◽  
Ashton S. Bradley ◽  
Mark A. Baker ◽  
...  
Keyword(s):  
Energy State ◽  
Topological Defects ◽  
High Energy ◽  
Einstein Condensate ◽  
Vortex Matter ◽  
Two Dimensional ◽  
Bose Einstein Condensate ◽  
Long Time ◽  
High Energy State ◽  
Bose Einstein

Adding energy to a system through transient stirring usually leads to more disorder. In contrast, point-like vortices in a bounded two-dimensional fluid are predicted to reorder above a certain energy, forming persistent vortex clusters. In this study, we experimentally realize these vortex clusters in a planar superfluid: a 87Rb Bose-Einstein condensate confined to an elliptical geometry. We demonstrate that the clusters persist for long time periods, maintaining the superfluid system in a high-energy state far from global equilibrium. Our experiments explore a regime of vortex matter at negative absolute temperatures and have relevance for the dynamics of topological defects, two-dimensional turbulence, and systems such as helium films, nonlinear optical materials, fermion superfluids, and quark-gluon plasmas.

Generating entangled state of Bose–Einstein condensate using electromagnetically induced transparency

2018 ◽  
Vol 32 (02) ◽  
pp. 1830001
Author(s):  
Song-Song Li
Keyword(s):  
Electromagnetically Induced Transparency ◽  
Einstein Condensate ◽  
Entangled State ◽  
Time Interval ◽  
Dynamical Process ◽  
Two Photon ◽  
Bose Einstein Condensate ◽  
Long Time ◽  
Bose Einstein ◽  
Induced Transparency

We put forward a scheme on how to generate entangled state of Bose–Einstein condensate (BEC) using electromagnetically induced transparency (EIT). It is shown that we can rapidly generate the entangled state in the dynamical process and the entangled state maintained a long time interval. It is also shown that the better entangled state can be generated by decreasing coupling strengths of two classical laser fields, increasing two-photon detuning and total number of atoms.

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