What is it about?
Polariton fluids made of coupled photonic and electronic oscillations have a polarization degree of freedom which can sustain both integer and half-integer quantized vortices. The photonic outcoupling makes possible to track their wavefunction, mapping both the density and phase in time by use of resonant ultrafast imaging.
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Why is it important?
Here we could for the first time directly set a polariton condensate carrying either a full or half vortex as initial condition to see their dynamical behavior. We show for the first time the spiraling of an half-vortex, and the branching of FV and HV as vortex lines in a 2D+t domain. We illustrate how the out-of-equilibrium nature of the polariton fluid results in that the vortex trajectories are not driven by intrinsic thermodynamic energy considerations, rather by a kinetic interplay of factors such as the nonlinearity and the disorder background with its associated polarization splitting.
Perspectives
Vortices in a quantum fluid must have an integer winding of the phase. On the one hand this work highlights the driving terms for the rich phenomenology of vortex dynamics in the nonlinear polariton fluid. This is consisting of spiraling, joint path, splitting and also the systematic couple generation of secondary vortices, always preserving the angular momentum. On the other hand, it is noteworthy how the vortex cores exhibit phase singularities which are both point-like and quantized. Hence there is a possible interesting analogy with elementary particles and their reactions such as merging and splitting, couple generation and annihilation. In this sense, such reactions are not driven by the localized particles 'per-sé', rather by the surrounding field due to the nonlinear fluid density, with the possible association of the background disorder to field fluctuations. The 2D+t trajectories of the vortex cores in the two-dimensional polariton fluid represent topological strings which will in the future highlight more complex structures such as closed loops or knots and help understanding the nature of cosmological- or subatomic-scale topology physics.
Dr Lorenzo Dominici
CNR NANOTEC, Institute of Nanotechnology
Read the Original
This page is a summary of: Vortex and half-vortex dynamics in a nonlinear spinor quantum fluid, Science Advances, December 2015, American Association for the Advancement of Science,
DOI: 10.1126/sciadv.1500807.
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Resources
Quantum vortex dynamics
The movies show the dynamics of the fluid density and phase, plus the 2D+t vortex lines of the main and secondary phase singularities. Both the half-vortex and full-vortex cases are reported, at different regimes. For a full description see the Sci Advances paper, http://advances.sciencemag.org/content/suppl/2015/12/01/1.11.e1500807.DC1
Polariton quantum vortex, ultraslow animation
The movie highlights an experimental polariton vortex coherently excited by a picosecond laser vorticant pulse as the initial condition of the planar polariton fluid and then left free to evolve. The ultrafast imaging corresponds to 1 ps / 1 s, which is a slowing down of 1.000.000.000.000 times of the polariton dynamics. The rotation at the optical frequency (in the order of the fs period) has been slowed further down by an additional ratio of several hundreds just to let the rotation be represented together with the vortex evolution in the order of the 10 ps lifetime of polaritons.
Quantized vorticity
Description of the experimental research on polariton fluids at the CNR NANOTEC.
Contributors
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