scholarly journals Symmetry Breaking in Interacting Ring-Shaped Superflows of Bose–Einstein Condensates

Symmetry ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 1312 ◽  
Author(s):  
Artem Oliinyk ◽  
Igor Yatsuta ◽  
Boris Malomed ◽  
Alexander Yakimenko
Keyword(s):  
Symmetry Breaking ◽  
Rotational Symmetry ◽  
Mean Field ◽  
Spontaneous Breaking ◽  
Persistent Currents ◽  
Mean Field Model ◽  
Final State ◽  
Double Ring ◽  
Angular Momenta ◽  
Bose Einstein

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.

scholarly journals Spontaneous symmetry breaking in persistent currents of spinor polaritons

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Evgeny Sedov ◽  
Sergey Arakelian ◽  
Alexey Kavokin
Keyword(s):  
Symmetry Breaking ◽  
Spontaneous Symmetry Breaking ◽  
Degrees Of Freedom ◽  
Continuous Wave ◽  
Rotational Symmetry ◽  
Einstein Condensate ◽  
Persistent Currents ◽  
Optical Pump ◽  
Bose Einstein Condensate ◽  
Bose Einstein

AbstractWe predict the spontaneous symmetry breaking in a spinor Bose–Einstein condensate of exciton-polaritons (polaritons) caused by the coupling of its spin and orbital degrees of freedom. We study a polariton condensate trapped in a ring-shaped effective potential with a broken rotational symmetry. We propose a realistic scheme of generating controllable spinor azimuthal persistent currents of polaritons in the trap under the continuous wave optical pump. We propose a new type of half-quantum circulating states in a spinor system characterized by azimuthal currents in both circular polarizations and a vortex in only one of the polarizations. The spontaneous symmetry breaking in the spinor polariton condensate that consists in the switching from co-winding to opposite-winding currents in opposite spin states is revealed. It is characterized by the change of the average orbital angular momentum of the condensate from zero to non-zero values. The radial displacement of the pump spot and the polarization of the pump act as the control parameters. The considered system exhibits a fundamental similarity to a superconducting flux qubit, which makes it highly promising for applications in quantum computing.

SYMMETRY BREAKING PHENOMENA IN MESOSCOPIC SYSTEMS: QUANTUM DOTS AND ROTATING NUCLEI

2009 ◽  
Vol 18 (04) ◽  
pp. 1014-1021
Author(s):  
R. G. NAZMITDINOV ◽  
A. PUENTE
Keyword(s):  
Quantum Dots ◽  
Symmetry Breaking ◽  
Rotational Symmetry ◽  
Random Phase ◽  
Mean Field ◽  
Rotating Frame ◽  
Octupole Deformation ◽  
The Mean ◽  
Symmetry Breaking Phenomena ◽  
Rotating Nuclei

A brief description of excited and ground states in two-dimensional quantum dots and rotating nuclei is presented within a mean field approach and a random-phase approximation (RPA). We discuss the procedure to restore the rotational symmetry broken at the mean field, which can be extended for other symmetry breaking cases. We propose to consider a disappearance of collective excitations in the rotating frame as a manifestation of symmetry breaking phenomena of the rotating mean field. In particular, we demonstrate that the disappearance of a collective octupole mode in the rotating frame in 162 Yb gives rise to the nonaxial octupole deformation.

scholarly journals Emergent $${{{{{{{\mathcal{PT}}}}}}}}$$-symmetry breaking of collective modes with topological critical phenomena

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Jian-Song Pan ◽  
Wei Yi ◽  
Jiangbin Gong
Keyword(s):  
Symmetry Breaking ◽  
Critical Point ◽  
Critical Phenomenon ◽  
Mean Field ◽  
Low Frequency ◽  
Spontaneous Breaking ◽  
Collective Modes ◽  
Spin Orbit Coupling ◽  
External Perturbations ◽  
Spectral Topology

AbstractThe spontaneous breaking of parity-time ($${{{{{{{\mathcal{PT}}}}}}}}$$ PT ) symmetry yields rich critical behavior in non-Hermitian systems, and has stimulated much interest, albeit most previous studies were performed within the single-particle or mean-field framework. Here, by studying the collective excitations of a Fermi superfluid with $${{{{{{{\mathcal{PT}}}}}}}}$$ PT -symmetric spin-orbit coupling, we uncover an emergent $${{{{{{{\mathcal{PT}}}}}}}}$$ PT -symmetry breaking in the Anderson-Bogoliubov (AB) collective modes, even as the superfluid ground state retains an unbroken $${{{{{{{\mathcal{PT}}}}}}}}$$ PT symmetry. The critical point of the transition is marked by a non-analytic kink in the speed of sound, which derives from the coalescence and annihilation of the AB mode and its hole partner, reminiscent of the particle-antiparticle annihilation. The system consequently becomes immune to low-frequency external perturbations at the critical point, a phenomenon associated with the spectral topology of the complex quasiparticle dispersion. This critical phenomenon offers a fascinating route toward perturbation-free quantum states.

scholarly journals On the characterization of vortex configurations in the steady rotating Bose–Einstein condensates

2017 ◽  
Vol 473 (2208) ◽  
pp. 20170602 ◽  
Author(s):  
P. G. Kevrekidis ◽  
D. E. Pelinovsky
Keyword(s):  
Field Model ◽  
Chemical Potential ◽  
Mean Field ◽  
Repulsive Interaction ◽  
Mean Field Model ◽  
Ode System ◽  
Steady Rotation ◽  
Bose Einstein ◽  
Good Agreement

Motivated by experiments in atomic Bose–Einstein condensates (BECs), we compare predictions of a system of ordinary differential equations (ODEs) for dynamics of one and two individual vortices in the rotating BECs with those of the Gross–Pitaevskii mean-field model written as a partial differential equation (PDE). In particular, we characterize orbitally stable vortex configurations in a symmetric harmonic trap due to a cubic repulsive interaction and a steady rotation. The ODE system is analysed in detail and the PDE model is approximated numerically. Good agreement between the two models is established in the semi-classical (Thomas–Fermi) limit that corresponds to the BECs at large values of the chemical potential.

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