| 摘要: | 受穩定但微弱的外力下，強作用的系統表現間歇性的山崩型反應，並在時空間中形成高關聯性之崩塌團簇，系統的強作用力不僅維持結構免於變化，也在結構變化時，傳遞區域能量至其他區域並引發時空間高關聯性之崩塌型事件，此現象廣泛存在於顆粒系統、受壓固體和地震系統等，其他強交互作用之系統。
接近凝固點附近的液體，其微觀結構並非不規則，結構以不同角度的晶塊所組成，晶塊不僅能承受外在壓力，且能在結構變化時釋放外力造成的能量，近期研究發現粒子受熱擾動激發，呈現集體性旋轉，並從大型晶塊分裂成小的旋轉晶塊，並重連恢復至更大型晶塊。受微弱的外力時，晶塊仍能穩定並在結構變化時傳遞外力之壓力至其他區域，並引發鍵斷裂。儘管如此，時空間的動力學、尺度、運動行為的分類與判定斷裂後短暫穩定的指標。我們以雷射光壓驅動電微粒懸浮於電漿所自組形成的冷液態微粒電漿為實驗平台，透過數位顯微追蹤微粒運軌跡探討上述重要議題。我們發現在結構重組時，時空間連結之晶格斷裂表現冪次分布，並分類為區域性之短暫爆發和連續性崩塌，而此分類起源於當結構重組時晶格斷裂誘發的缺陷對群之傳遞並碰撞時，缺陷對群之Burgers 向量是否相消，相消時使斷裂事件呈現短暫爆發並伴隨寧靜和整齊晶格排列，反之導致區域性高應力誘發連續性之崩塌型結構重組。
;Under weak external stress, intermittent emergent responses in the form of avalanche type spatiotemporal clusters are ubiquitous phenomena in strongly coupled systems, such as granular systems, stressed solids, and seismic systems. The strong coupling not only sustains the structure from structural rearrangement but also spreads the local strain energy to remote regions inducing spatiotemporally correlated clusters once the accumulated local strain energy goes beyond a certain threshold.
Unlike solids, under weak external stress, liquids exhibit plastic deformation. The local strain energy cannot accumulate and is rapidly relaxed through structural rearrangement. However, unlike the intuitive expectation, a cold liquid around freezing under weaker thermal agitations is not completely disordered. It possesses a patchwork of crystalline ordered domains (CODs), which not only sustains the local strain energy but also releases the energy through structural rearrangement. Recent studies showed that the thermal-excited structural rearrangement exhibits cooperative excitation hopping in the form of co-rotating CODs, which ruptures the large CODs into small CODs followed by healing back to large CODs, and that, under weak external stress, CODs can temporarily sustain and propagate the local stress to remote regions that further initiates the bond cracking near defects. Nevertheless, the generic spatiotemporal dynamics, the scaling behaviors and the kinetic classification of the cracking, and the alarms for warning the short quiescent period between cracking bursts, are still unexplored issues.
In this work, we experimentally investigate spatiotemporal dynamical behaviors of the avalanche type structural rearrangement through cracking-healing processes in a weakly stressed dusty plasma cold liquid. It is found that the cracking cluster size in xyt space follows power law distribution. The histograms of the cracking burst and quiescent time periods between cracking, and the persistent times maintaining ordered and disordered structures all follow power law scaling behaviors. The temporal cracking behavior can be classified into single burst and successive cracking burst fluctuation. Kinetically, a COD is ruptured by cracking lines through co-rotating domains, which induce dislocation propagation into the region. If the directions of the Burgers vectors of incoming dislocations allow dislocation annihilation, deteriorated structure anneals into a large COD. If the directions of Burgers vectors forbid the annihilation process, the structure needs successive cracking behavior to resume a better structural order. The low regional structural order at the end of a cracking burst can be regarded as an alarm for predicting a short quiescent time period before the next cracking burst. |
