How to fix a broken symmetry: Quantum dynamics of symmetry restoration in a ferromagnetic Bose-Einstein condensate

Abstract

We discuss the dynamics of a quantum phase transition in a spin-1 Bose-Einstein condensate when it is driven from the magnetized broken-symmetry phase to the unmagnetized ``symmetric'' polar phase. We determine where the condensate goes out of equilibrium as it approaches the critical point, and compute the condensate magnetization at the critical point. This is done within a quantum Kibble-Zurek scheme traditionally employed in the context of symmetry-breaking quantum phase transitions. Then we study the influence of the nonequilibrium dynamics near a critical point on the condensate magnetization. In particular, when the quench stops at the critical point, nonlinear oscillations of magnetization occur. They are characterized by a period and an amplitude that are inversely proportional. If we keep driving the condensate far away from the critical point through the unmagnetized ``symmetric'' polar phase, the amplitude of magnetization oscillations slowly decreases reaching a non-zero asymptotic value. That process is described by the equation that can be mapped onto the classical mechanical problem of a particle moving under the influence of harmonic and ``anti-friction'' forces whose interplay leads to surprisingly simple fixed-amplitude oscillations. We obtain several scaling results relating the condensate magnetization to the quench rate, and verify numerically all analytical predictions.

15 pages, 11 figures, final version accepted in NJP (slight changes with respect to the former submission)

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Cited by in corpus (6)

• Exploring the Kibble-Zurek mechanism with homogeneous Bose gases
• Phase Transition in Space: How Far Does a Symmetry Bend Before It Breaks?
• Thermodynamics in expanding shell-shaped Bose-Einstein condensates
• Locating quantum critical points with Kibble-Zurek quenches
• Kibble-Zurek scaling due to environment temperature quench in the transverse field Ising model
• Fast generation of time-stationary spin-1 squeezed states by non-adiabatic control