Special Issue "Symmetry Breaking in Bose-Einstein Condensates"

A special issue of Symmetry (ISSN 2073-8994).

Deadline for manuscript submissions: 31 December 2019.

Special Issue Editor

Prof. Dr. Luca Salasnich
E-Mail Website
Guest Editor
Department of Physics and Astronomy "Galileo Galilei", University of Padova, Via Marzolo 8, 35131 Padova, Italy
Tel. +39 049 827 7132
Interests: Bose-Einstein condensation; Bose-Einstein condensation; ultracold atoms; quantum statistical physics
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Special Issue Information

Dear Colleagues,

Bose-Einstein condensation is usually associated with spontaneous symmetry breaking (SSB) and off-diagonal long-range order (ODLRO). However, in systems with reduced dimensionality, quantum fluctuations make the SSB and ODLRO concepts more elusive, and new paradigms, such as quantum phase transition, quasi-condensate, and topological order, are needed. These new paradigms are also expected to play a crucial role in the presence of disorder, multi-components, Bose-Fermi mixtures, spin-orbit and Rabi couplings, long-range interaction potentials, and exotic confinements. The objective of the present Special Issue is to publish original papers and reviews which adequately represent the ongoing progress in this vast research area.

Prof. Dr. Luca Salasnich
Guest Editor

Manuscript Submission Information

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Keywords

  • Off-diagonal long-range order
  • Quantum phase transition
  • Quasi-condensate
  • Topological order
  • Disorder
  • Multi-components
  • Bose-Fermi mixtures
  • Spin-orbit
  • Long-range interaction.

Published Papers (3 papers)

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Research

Open AccessArticle
Symmetry Breaking in Interacting Ring-Shaped Superflows of Bose–Einstein Condensates
Symmetry 2019, 11(10), 1312; https://doi.org/10.3390/sym11101312 - 19 Oct 2019
Abstract
We demonstrate that the evolution of superflows in interacting persistent currents of ultracold gases is strongly affected by symmetry breaking of the quantum vortex dynamics. We study counter-propagating superflows in a system of two parallel rings in regimes of weak (a Josephson junction [...] Read more.
We demonstrate that the evolution of superflows in interacting persistent currents of ultracold gases is strongly affected by symmetry breaking of the quantum vortex dynamics. We study counter-propagating superflows in a system of two parallel rings in regimes of weak (a Josephson junction with tunneling through the barrier) and strong (rings merging across a reduced barrier) interactions. For the weakly interacting toroidal Bose–Einstein condensates, formation of rotational fluxons (Josephson vortices) is associated with spontaneous breaking of the rotational symmetry of the tunneling superflows. The influence of a controllable symmetry breaking on the final state of the merging counter-propagating superflows is investigated in the framework of a weakly dissipative mean-field model. It is demonstrated that the population imbalance between the merging flows and the breaking of the underlying rotational symmetry can drive the double-ring system to final states with different angular momenta. Full article
(This article belongs to the Special Issue Symmetry Breaking in Bose-Einstein Condensates)
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Open AccessArticle
Faraday and Resonant Waves in Dipolar Cigar-Shaped Bose-Einstein Condensates
Symmetry 2019, 11(9), 1090; https://doi.org/10.3390/sym11091090 - 01 Sep 2019
Abstract
Faraday and resonant density waves emerge in Bose-Einstein condensates as a result of harmonic driving of the system. They represent nonlinear excitations and are generated due to the interaction-induced coupling of collective oscillation modes and the existence of parametric resonances. Using a mean-field [...] Read more.
Faraday and resonant density waves emerge in Bose-Einstein condensates as a result of harmonic driving of the system. They represent nonlinear excitations and are generated due to the interaction-induced coupling of collective oscillation modes and the existence of parametric resonances. Using a mean-field variational and a full numerical approach, we studied density waves in dipolar condensates at zero temperature, where breaking of the symmetry due to anisotropy of the dipole-dipole interaction (DDI) plays an important role. We derived variational equations of motion for the dynamics of a driven dipolar system and identify the most unstable modes that correspond to the Faraday and resonant waves. Based on this, we derived the analytical expressions for spatial periods of both types of density waves as functions of the contact and the DDI strength. We compared the obtained variational results with the results of extensive numerical simulations that solve the dipolar Gross-Pitaevskii equation in 3D, and found a very good agreement. Full article
(This article belongs to the Special Issue Symmetry Breaking in Bose-Einstein Condensates)
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Open AccessArticle
Correlation Dynamics of Dipolar Bosons in 1D Triple Well Optical Lattice
Symmetry 2019, 11(7), 909; https://doi.org/10.3390/sym11070909 - 12 Jul 2019
Abstract
The concept of spontaneous symmetry breaking and off-diagonal long-range order (ODLRO) are associated with Bose–Einstein condensation. However, as in the system of reduced dimension the effect of quantum fluctuation is dominating, the concept of ODLRO becomes more interesting, especially for the long-range interaction. [...] Read more.
The concept of spontaneous symmetry breaking and off-diagonal long-range order (ODLRO) are associated with Bose–Einstein condensation. However, as in the system of reduced dimension the effect of quantum fluctuation is dominating, the concept of ODLRO becomes more interesting, especially for the long-range interaction. In the present manuscript, we study the correlation dynamics triggered by lattice depth quench in a system of three dipolar bosons in a 1D triple-well optical lattice from the first principle using the multiconfigurational time-dependent Hartree method for bosons (MCTDHB). Our main motivation is to explore how ODLRO develops and decays with time when the system is brought out-of-equilibrium by a sudden change in the lattice depth. We compare results of dipolar bosons with contact interaction. For forward quench ( V f > V i ) , the system exhibits the collapse–revival dynamics in the time evolution of normalized first- and second-order Glauber’s correlation function, time evolution of Shannon information entropy both for the contact as well as for the dipolar interaction which is reminiscent of the one observed in Greiner’s experiment [Nature, 415 (2002)]. We define the collapse and revival time ratio as the figure of merit ( τ ) which can uniquely distinguish the timescale of dynamics for dipolar interaction from that of contact interaction. In the reverse quench process ( V i > V f ) , for dipolar interaction, the dynamics is complex and the system does not exhibit any definite time scale of evolution, whereas the system with contact interaction exhibits collapse–revival dynamics with a definite time-scale. The long-range repulsive tail in the dipolar interaction inhibits the spreading of correlation across the lattice sites. Full article
(This article belongs to the Special Issue Symmetry Breaking in Bose-Einstein Condensates)
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