| dc.description.abstract | Under strong external drive, macroscopic wave turbulence with a continuous power spectrum ubiquitously occurs in various nonlinear continuous media, such as water surface, chemical systems, nonlinear optical media, and plasmas. Previous studies mainly focused on dynamical behaviors such as dispersion relations, scaling behaviors, energy cascades, non-Gaussian behaviors, and multifractalities, but have paid less attention on the spatiotemporal coherent behaviors at various scales. Beyond the continuous limit, whether thermally excited microscopic acoustic wave turbulence occurs, and the corresponding spatiotemporal coherent behaviors at various scales at the discrete level still remain open fundamental issues.
Microscopically, the cold liquid around freezing is a nonlinear discrete many-body system. The competition between mutual interaction and thermal agitation leads to the crystalline ordered domains (CODs) with different lattice orientations surrounded with defects. Waves are allowed to propagate in CODs. However, those waves have never been investigated from the wave turbulence view, especially their spatiotemporal coherence at different scales.
In this work, we experimentally demonstrate the observation of thermally excited microscopic acoustic wave turbulence at the discrete level in a quasi-2D cold dusty plasma liquid formed by negatively charged micro-meter sized particle suspended in a low pressure Ar discharge. Through multidimensional complementary ensemble empirical mode decomposition from Hilbert-Huang transform, the relative transverse displacement of dust particle with continuous power spectrum is decomposed into several traveling wave modes with different spatiotemporal scales. It is found that all coherent wave modes exhibit intermittent excitation, propagation, scattering, and annihilation in the form of clusters in the xyt space. Their cluster size distributions rescaled by their own spatiotemporal scales collapse into a single power-law distribution, which manifests the self-similar behavior of different wave modes, akin to the self-similar dynamics of coherent excitations in other nonlinear systems. The poor particle interlocking in the region with poor structural order allows easier excitations of the slow modes with large envelope, which leads to the positive correlation between the envelopes of adjacent modes. The sudden spatiotemporal phase synchronization of slow wave modes with large envelopes can switch the particle motion from cage rattling to cooperative hopping.
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