Abstract
Quantum turbulence deals with the phenomenon of turbulence in quantum fluids, such as superfluid helium and trapped Bose-Einstein condensates (BECs). Although much progress has been made in understanding quantum turbulence, several fundamental questions remain to be answered. In this work, we investigated the entropy of a trapped BEC in several regimes, including equilibrium, small excitations, the onset of turbulence, and a turbulent state. We considered the time evolution when the system is perturbed and let to evolve after the external excitation is turned off. We derived an expression for the entropy consistent with the accessible experimental data, which is, using the assumption that the momentum distribution is well-known. We related the excitation amplitude to different stages of the perturbed system, and we found distinct features of the entropy in each of them. In particular, we observed a sudden increase in the entropy following the establishment of a particle cascade. We argue that entropy and related quantities can be used to investigate and characterize quantum turbulence.
Highlights
The route to equilibration of a many-body quantum system driven to a far-from-equilibrium state is a question that permeates several areas in physics
Turbulence in quantum fluids might be more tractable than its classical counterpart, because the vortex circulation is quantized in the former and continuous for classical fluids
We calculated the entropy of a Bose–Einstein condensates (BECs) in regimes that go from an unperturbed system up to a turbulent cloud, corresponding to a far-from-equilibrium state
Summary
The route to equilibration of a many-body quantum system driven to a far-from-equilibrium state is a question that permeates several areas in physics. Quantum turbulence [1,2] is an example of such out-of-equilibrium systems. Classical turbulence, is a process that occurs in many types of fluids, spanning the climatic effects that involve large masses down to capillaries. It is characterized by a large number of degrees of freedom interacting non-linearly to produce disordered states, both in space and time. Turbulence in quantum fluids might be more tractable than its classical counterpart, because the vortex circulation is quantized in the former and continuous for classical fluids. The advances in trapping, cooling, and tuning the interparticle interactions in atomic Bose–Einstein condensates (BECs) make them excellent candidates for studying quantum turbulence
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