2011/03/31 by Luca Pezzè, L. Pezze, Martin Robert-De-Saint-Vincent +15 · 1 citation
Physics and Astronomy · #Anisotropic diffusion #Anisotropy #Anomalous diffusion #Cold Atom Physics and Bose-Einstein Condensates #Diffusion #Gaussian #Particle (ecology) #Physics #Quantum mechanics #Quantum, superfluid, helium dynamics #Statistical physics #Theoretical and Computational Physics #Thermal #Thermodynamics #cond-mat.quant-gas
paper · pdf · doi:10.1088/1367-2630/13/9/095015
published as New J. Phys. 13, 095015 (2011) · 19 pages, 16 figures
openalex publication_date 2011/09/26 · arxiv created 2011/10/07 · arxiv updated 2015/05/27 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We numerically study the dynamics of cold atoms in a two-dimensional disordered potential. We consider an anisotropic speckle potential and focus on the classical dynamics, which is relevant to some recent experiments. Firstly, we study the behavior of particles with a fixed energy and identify different transport regimes. For low energy, the particles are classically localized due to the absence of a percolating cluster. For high energy, the particles undergo normal diffusion and we show that the diffusion coefficients scale algebraically with the particle energy, with an anisotropy factor which significantly differs from that of the disordered potential. For intermediate energy, we find a transient sub-diffusive regime, which is relevant to the time scale of typical experiments. Secondly, we study the behavior of a cold-atomic gas with an arbitrary energy distribution, using the above results as a groundwork. We show that the density profile of the atomic cloud in the diffusion regime is strongly peaked and, in particular, that it is not Gaussian. Its behavior at large distances allows us to extract the energy-dependent diffusion coefficients from experimental density distributions. For a thermal cloud released into the disordered potential, we show that our numerical predictions are in agreement with experimental findings. Not only does this work give insights to recent experimental results, but it may also serve interpretation of future experiments searching for