Synthetic dissipation and cascade fluxes in a turbulent quantum gas

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Navon, Nir 
Zhang, Jinyi 
Lopes, Raphael 
Gaunt, Alexander L 

Scale-invariant fluxes are the defining property of turbulent cascades, but their direct measurement is a notorious problem. Here we perform such a measurement for a direct energy cascade in a turbulent quantum gas. Using a time-periodic force, we inject energy at a large lengthscale and generate a cascade in a uniformly-trapped Bose gas. The adjustable trap depth provides a high-momentum cutoff kD, which realises a synthetic dissipation scale. This gives us direct access to the particle flux across a momentum shell of radius kD, and the tunability of kD allows for a clear demonstration of the zeroth law of turbulence. Moreover, our time-resolved measurements give unique access to the pre-steady-state dynamics, when the cascade front propagates in momentum space.

cond-mat.quant-gas, cond-mat.quant-gas, cond-mat.stat-mech, physics.atom-ph, physics.flu-dyn, quant-ph
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American Association for the Advancement of Science
Engineering and Physical Sciences Research Council (EP/P009565/1)
Engineering and Physical Sciences Research Council (EP/N011759/1)
Engineering and Physical Sciences Research Council (EP/R043396/1)
European Research Council (682285)
This work was supported by EPSRC [Grants No. EP/N011759/1 and No. EP/P009565/1], ERC (QBox), QuantERA (NAQUAS, EPSRC Grant No. EP/R043396/1), AFOSR, and ARO. N.N. acknowledges support from Trinity College (Cambridge) and the David and Lucile Packard Foundation. R.L. acknowledges support from the E.U. Marie-Curie program [Grant No. MSCA-IF-2015 704832] and Churchill College, Cambridge. R.P.S. acknowledges support from the Royal Society. K.F. was supported by JSPS KAKENHI Grant No. JP16J01683. M.T. acknowledges support from JSPS KAKENHI Grant No. 17K05548 and MEXT KAKENHI Grant No. 16H00807.
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