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3. July 2017 11:30

Phase ordering dynamics and weak wave turbulence in a ferromagnetic spin-1 Bose-Einstein condensate

Lewis Williamson
The Jack Dodd Centre for Quantum Technology, University of Otago, Dunedin, New Zealand

Spinor Bose-Einstein condensates exhibit both superfluid and magnetic order, and accommodate phases with rich symmetry properties and topological defects. Transitions between these phases can be induced by tuning external fields. This system has proved ideal for studying non-equilibrium quench dynamics in both experimental and theoretical studies. In this talk I will discuss simulations of order formation in a quasi-2D spin-1 ferromagnetic condensate following a quench from an unmagnetised phase to one of three ferromagnetic phases, each with distinct symmetry properties (easy-plane, easy-axis or isotropic). I will firstly review results on the scale invariant growth of order associated with topological defect annihilation. I will then discuss recent results on weak wave turbulence identified in the easy-plane phase. This turbulence drives energy from long wavelength spin waves to a short wavelength thermalised field. The shape of the cascade in momentum space moves to longer wavelengths in a scale invariant way across time scales much longer than the time scale of topological defect annihilation. This surprising result highlights the role that turbulence can play in conservative phase ordering, and suggests the presence of a second nonthermal fixed point in the non-equilibrium dynamics.