Abstract:
We investigate anomalously slow coarsening in a dilute two-dimensional superfluid closed with respect to particle and energy exchange with the environment. The dynamics is demonstrated to be closely connected both to a nonthermal fixed point (NTFP) in a far-from-equilibrium quantum system and to Kraichnan-Kolmogorov turbulence. During a universal dynamical regime associated with an anomalous NTFP, vortex dynamics are understood to be governed by three-vortex collisions that trigger vortex-antivortex annihilation events, leading to a subdiffusive decay of the vortex density and thus growth of the characteristic interdefect length scale, ℓv∼𝑡𝛽 with 𝛽≈1/5. It is found that, during the same time when this power law in time is seen, the moments of the superfluid velocity circulation Γ around an area of spatial extent 𝑟 exhibit power-law scaling Γ2(𝑟)∼𝑟8/3, in agreement with Kraichnan-Kolmogorov predictions for an inverse energy cascade in the inertial range, in a driven-open setting. Moreover, in high-order moments, intermittent deviations from linear scaling Γ2𝑝(𝑟)∼[Γ2(𝑟)]𝑝 are observed that are consistent with bifractal intermittency corrections previously measured in fully developed classical turbulence. These results establish a quantitative link between decaying quantum turbulence in a closed superfluid and universal dynamics near a nonthermal fixed point. Notably, the subdiffusive decay exponent 𝛽≈1/5 deviates significantly from values reported for classical systems.
N. Rasch, T. Gasenzer, „Decaying superfluid turbulence near an anomalous nonthermal fixed point“, Phys. Rev. A 113, L051302 (2026).
https://journals.aps.org/pra/abstract/10.1103/p6wv-z621
Related to Project A04, A07