Fluctuation-induced and symmetry-prohibited metastabilities in spinor Bose-Einstein condensates

We present a comprehensive analysis of the emerging order and chaos and enduring symmetries, accompanying a generic (high-barrier) first-order quantum phase transition (QPT). The interacting boson model Hamiltonian employed, describes a QPT between spherical and deformed shapes, associated with its U(5) and SU(3) dynamical symmetry limits. A classical analysis of the intrinsic dynamics reveals a rich but simply-divided phase space structure with a Hénon-Heiles type of chaotic dynamics ascribed to the spherical minimum and a robustly regular dynamics ascribed to the deformed minimum. The simple pattern of mixed but well-separated dynamics persists in the coexistence region and traces the crossing of the two minima in the Landau potential. A quantum analysis discloses a number of regular lowenergy U(5)-like multiplets in the spherical region, and regular SU(3)-like rotational bands extending to high energies and angular momenta, in the deformed region. These two kinds of regular subsets of states retain their identity amidst a complicated environment of other states and both occur in the coexistence region. A symmetry analysis of their wave functions shows that they are associated with partial U(5) dynamical symmetry (PDS) and SU(3) quasi-dynamical symmetry (QDS), respectively. The pattern of mixed but well-separated dynamics and the PDS or QDS characterization of the remaining regularity, appear to be robust throughout the QPT. Effects of kinetic collective rotational terms, which may disrupt this simple pattern, are considered.

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“…(18). Each panel depicts the n d -probability, P (L i ) n d , for states in the multiplet and lists the energy of a representative eigenstate.…”

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confidence: 99%

First-order quantum phase transitions: Test ground for emergent chaoticity, regularity and persisting symmetries

Macek

Leviatan

2014

Annals of Physics

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“…These interactions are quite weak for the case of 87 Rb, but can have an appreciable role on the low-energy spectrum, which would affect large-cell fluctuation measurements (also see [49]). Finally, beyond the Bogoliubov approach we presented here there are many avenues for extending the theory including the role of quantum and thermal back-action on the condensate [50,51] and detailed behavior of the system near phase boundaries (e.g., see [52][53][54][55][56][57]). …”

Section: Discussionmentioning

confidence: 99%

Fluctuations of spinor Bose-Einstein condensates

2014

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We develop theory for fluctuations in atom number and spin within finite-sized cells of a spinor Bose-Einstein condensate. This theory provides a model of measurements that can be performed in current experiments using finite resolution in situ imaging. We develop analytic results for quantum and thermodynamic limits of the fluctuations and apply our theory to the four equilibrium phases of a spin-1 condensate. We then validate these limits and examine the behaviour over a wide parameter regime using numerical calculations specialised to the case of a spinor condensate confined to be quasi-two-dimensional (quasi-2D).Comment: 11 pages, 9 figure

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“…Owing the non-continuity of the order-parameters, both phases may remain stable, whereas the ground state is given by the lowest energy state. Consequently, near the phase boundaries may exist metastable phases [15][16][17][18][19][20][21] which play a crucial role in a variety of phenomena such as quantum tunneling [22,23], domain formations [24,25], and quench dynamics [26][27][28], among others [29,30]. In particular, recent experiments have reported the observation of dynamical quantum phase transitions under different types of quench dynamics in an antiferromagnetic spinor BEC [28], including a more recent experiment that involves a phase transition between excited states [31].…”

Section: Introductionmentioning

confidence: 99%

Metastable spin-phase diagrams in antiferromagnetic Bose-Einstein condensates

Serrano-Ensástiga,

Mireles

2021

Preprint

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Spinor Bose-Einstein condensates under external magnetic fields exhibit well-characterized spin domains of its ground state due to spin-dependent interactions. At low temperatures, collisioninduced spin-mixing instabilities may promote the condensate to dwell into metastable states occurring near the phase boundaries. In this work, we study theoretically the metastable spin-phase diagram of a spin-1 antiferromagnetic Bose-Einstein condensate at zero and finite temperatures. The approach makes use of Hartree-Fock theory and exploits the symmetry of the Hamiltonian and of the order parameters yielding a closed system of transcendental equations for the free energy, fully avoiding the use of selfconsistency. Our results are consistent with recent experiments and allow us to explain qualitatively the different types of observed quench dynamics. In addition, we found that similar phenomena should occur in antiferromagnetic spinor condensates with a sudden change in the temperature. It is shown also that the increase of temperature induces a traceable shift of the Ferromagnetic-Polar transition boundary, behavior previously not noticed by selfconsistent mean-field calculations.

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Fluctuation-induced and symmetry-prohibited metastabilities in spinor Bose-Einstein condensates

Cited by 17 publications

References 47 publications

First-order quantum phase transitions: Test ground for emergent chaoticity, regularity and persisting symmetries

First-order quantum phase transitions: Test ground for emergent chaoticity, regularity and persisting symmetries

Fluctuations of spinor Bose-Einstein condensates

Metastable spin-phase diagrams in antiferromagnetic Bose-Einstein condensates

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