Self-excited vortical waves in layering Yukawa solids

Chen-Yu Siao^1*, Wei-Shuo Lo¹, Lin I¹

¹Department of Physics, National Central University, Taoyuan City, Taiwan

* Presenter:Chen-Yu Siao, email:chenyusiao@g.ncu.edu.tw

Crystalline solids can support longitudinal and transverse wave propagation due to their ordered lattice structure, sustaining shear stress up to their yield point. Below the melting point, thermal fluctuations are regarded as disordered sources that randomly excite and de-excite multiscale waves. The propagation and superposition of those waves with uncertain phases and amplitude might lead to excitations of multiscale coherent spatiotemporal structures. In this work, we numerically investigate the multiscale coherent excitations in a three-dimensional Yukawa crystal confined in a mesoscopic gap. In this system, the tight boundary confinement breaks the system symmetry. It causes the formation of a stack of layers with intralayer triangular lattice, parallel to the confinement boundaries, which support the easier excitation of long wave length intralayer vibrational wave, but suppress the long wave length interlayer vibrations. Particle motion is decomposed into multiscale modes through Multi-dimensional complementary ensemble empirical mode decomposition (MCEEMD). It is found that intralayer excitation can be viewed as a collection of multiscale vortical waves which exhibit a disordered array of vortices with spatially alternating signs of vorticity and temporally varying vortex shapes and strengths. Through interlayer coupling, the coherent intralayer excitations of adjacent layers are strongly correlated which leads to the formation of a disordered array of wiggling vortex core filaments.

Keywords: acoustic wave, wave vortex, layering Yukawa solid