EXCITATION OF A TRAPPED BEC: GENERATION OF TURBULENCE AND ITS - - PowerPoint PPT Presentation

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EXCITATION OF A TRAPPED BEC: GENERATION OF TURBULENCE AND ITS - - PowerPoint PPT Presentation

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EXCITATION OF A TRAPPED BEC: GENERATION OF TURBULENCE AND ITS CHARACTERIZATION Dr. Mnica A. Caracanhas (V.S. Bagnato) University of So Paulo Brazil Critical Stability 2014 External Collaborators: Prof. V. Yukalov (Dubna) G. Roati

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  • Dr. Mônica A. Caracanhas

(V.S. Bagnato) University of São Paulo Brazil

Critical Stability 2014

EXCITATION OF A TRAPPED BEC: GENERATION OF TURBULENCE AND ITS CHARACTERIZATION

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External Collaborators:

  • Prof. V. Yukalov (Dubna)
  • G. Roati (Florence)
  • A. Novikov (Dubna)
  • Prof. A. Fetter (Stanford)
  • Prof. M. Tsubota (Osaka)

Part of the Group:

  • Prof. E. Henn
  • F. Poveda-Cuevas, P. Castilho, P. Tavares, R. Poliseli, E. Pedroso,
  • F. Vivanco, A. Smaira, A. Cidrim, A. Fritsch, A. Bahrami

K.. Magalhães, G. Telles, M. Caracanhas

  • E. Santos, M. Tsatsos
  • 3 BEC experiments: Rb-I, Rb-II, Na/K
  • Theory group
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SUPERFLUIDITY - BEC

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In atomic BEC Experimental: generate and characterize Theory: New possibilities to generate QT

QT

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Displacement, Rotation and Deformation of the potential ADDITION OF “SHAKING” COILS

EXCITATION BY OSCILLATION OF THE POTENTIAL

Atomic washing machine

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PRODUCING BEC (1 min) EXCITATION ( 0 to 70 ms ) Time and amplitude HOLDING TIME (20 ms) TOF FOLLOWED BY ABSORPTION IMAGE

EXPERIMENTAL SEQUENCE

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  • Las. Phys. Lett. 8,691 (2011).
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Dubna – Bogoliubov Inst.

  • Las. Phys. Lett., v.11, 8 jun 2014.
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VORTEX FORMATION

  • J. Low. Temp. Phys. 158, 435-442 (2010).
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EVOLUTION TO TURBULENCE

Drop  decay to granulation

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4 6 8 10 12 14 16 0,6 0,8 1,0 1,2 1,4

Turbulent cloud Regular BEC cloud Thermal cloud

Aspect ratio

TOF (ms)

Thermal BEC Turbulent

Cloud expansion as identification

  • f QT
  • J. Phys. Conf. Ser. 264,012004 (2011), J. Low Temp. Phys. 170, 133 (2013).
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Energy is injected at large scale ( vortex filaments) Special configuration ( Turbulence ) Reconnection allow energy to flow to small scale (Kelvin cascade) Phonon Emission (equivalent to effective kinematic viscosity)

QT

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  • M. Kobayashi and M. Tsubota, PRL94,065302 (2005), JPSJ 74, 3248 (2005).
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  • B. Nowak et al (arXiv: 1012.4437)

MOMENTUM SPECTRUM

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HOW TO OBTAIN n(k) in a trapped superfluid?

Time dependence on the free expansion

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Interactions vs kinetic Self-similar  kinetic Lower density  kinetic

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VALIDITY

k2 k1

K2 - largest k  cut off : 3 107 m-1 K1 - about 1.5 107 m-1

Laser Phys. Lett., 11, 015501 (2014).

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K-3

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Direct versus inversed cascade : 3D versus 2D Time evolution

COLLECTIVE MODES

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Demonstration of direct cascade of energy…..

k

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arXiv:1405.0992 [cond-mat.quant-gas]

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SPONTANEOUS GENERATION OF TURBULENCE

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Kolmogorov: In the inertial sub-range, no dissipation and local interactions

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