Screw dislocations in the transient relaxation of confinement-induced layering of Yukawa liquids after quenching

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/92590

Title:	Screw dislocations in the transient relaxation of confinement-induced layering of Yukawa liquids after quenching
Authors:	張允瑄;Zhang, Yun-Xuan
Contributors:	物理學系
Keywords:	螺旋差排缺陷絲;焠冷 Yukawa 液體;平面邊界誘導層化結構
Date:	2023-11-16
Issue Date:	2024-09-19 15:56:26 (UTC+8)
Publisher:	國立中央大學
Abstract:	在平面邊界的侷限下，微觀三維液體沿著形成層狀有序結構。瞬間焠冷液體至凝固點附近可使表面層化影響傳至三維液體內部，形成多層堆疊之有序結構，但熱擾動仍能破壞層狀結構。然而，儘管過去對微觀結構、微觀運動和與體積液體不同的黏彈性響應進行了深入研究，但在淬冷後的弛豫過程動力行為，及在此過程中螺旋差排缺陷(screw dislocations)如何產生與湮滅之動力行為，仍然是一個挑戰性問題。螺旋差排缺陷是一種繞著螺旋前沿纏繞的絲狀拓撲缺陷，它們在分層系統中隨處可見，如分層固體和弱擾動的非穩平面波。然而，由於前者為固體，無法通過其研究螺旋差排缺陷動力行為，而後者的高波速則使其難以觀察，因此螺旋差排缺陷的通用動力學行為仍然難以捉摸。本研究透過分子動力學電腦模擬，利用二邊界平面侷限下焠冷後的冷 Yukawa 液體對上述議題進行研究。研究以粗粒化程式建構三維微粒密度之時空演變，確定螺旋差排缺陷的位置。數值上證明了在淬冷後限制誘導層狀結構的弛豫過程中觀察到了具有非凍結動力學並自發生成的螺旋差排缺陷；更揭示了它們的動力學行為和拓撲起源。我們首度觀察到空間中可形成具對偶缺陷絲的缺陷環(defect loop)，或W 形狀多條交替對偶缺陷絲所構成的大型缺陷環。在淬冷後，缺陷絲的數目隨弛豫時間的增長而緩減。熱擾動所產生的粒子層扭動不穩定性(undulation instability) 的時空增長和衰減，可誘發層面在小尺度扭折(kink)，進而造成一連串相鄰層面的破裂與重連，形成在撕裂-重連線二端點被相反旋轉層面方向所環繞的對偶螺旋缺陷絲產生之主因。而相反的機制可使二對偶缺陷絲湮滅。粒子層扭動不穩定性也對缺陷環或缺陷絲之小尺度波動(fluctuation)具有關鍵作用。此外，二相靠近具有相反或相同螺旋性的缺陷絲可斷裂與重連，進而導致新的分離二缺陷環的形成與其相反程序，從而使缺陷環分裂或合併。此實驗之重要發現，可供建構具層狀結構之非穩系統中，如固體、非穩平面波中螺旋缺陷絲動力行為與其交互作用之普世機制。;For liquids in a tight gap, the two flat boundaries can suppress transverse particle motion and induce layered structure. Nevertheless, regardless of the past intensive studies on the micro-structure, micro-motion, and viscoelastic response deviating from those of the bulk liquid, the layering dynamics in its transient relaxation after quenching remains an elusive challenging issue, especially from the perspective of screw dislocations. Screw dislocations (SDs) are filament-like topological defects winded around by helical fronts. They are omnipresent in layered systems such as layered solids and weakly disordered traveling waves. Nevertheless, the generic dynamical behaviors of SDs remain elusive because the former usually exhibit frozen dynamics and high wave speed, while the latter makes them difficult to observe. Here, using the confined liquid after quenching as a platform, we numerically demonstrate the observation of spontaneously generated SDs with unfrozen dynamics in the transient relaxation of confinement-induced layering; and unravel their generic dynamical behaviors and topological origins. It is found that the total number of SDs decreases and levels off with increasing time after quenching. The spatiotemporal growth and decay of layer undulation instability, which causes the layer kinking/rupturing/reconnection, play a crucial role in forming fluctuating SD loops or strings of connected SD filaments (SDFs) with alternative helicities. In addition, the breaking/reconnection of approaching SDFs with opposite or same helicities leads to the formation of new separated SDFs, resulting in the shedding or pinching of SD loops.
Appears in Collections:	[Graduate Institute of Physics] Electronic Thesis & Dissertation

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