"Is diffusion anomalous in two-dimensional Yukawa liquids?"


Artikel der AG Bonitz am 3.11.2009 in Physical Review Letters erschienen.

Over the last 10 years there have been many experimental and theoretical studies on transport properties of (quasi) two-dimensional plasmas. The reason are early predictions of enhanced diffusion ("superdiffusion") compared to three-dimensional systems. However, the results were contradicting each other, and no systematic study of the time dependence was presented so far. The present paper fills this gap. It shows how the strength of superdiffusion depends on the interaction range, on the strength of correlations in the system and on dissipation. Most importantly, it is found that the existence of superdiffusion crucially depends on the dissipation and on the time scale of the measurement: at short times the system may be superdiffusive or subdiffusive, depending on the friction. However, for sufficiently long times, diffusion returns to normal. The figure shows the diffusion exponent (it equals 1 for normal diffusion and is larger than one for superdiffusion) as a function of dissipation and time.