層狀二類超導體在磁場中的傳輸行為

Abstract

我利用2 維time – dependent Ginzburg – Landau 方程式來模擬計算出動態和靜態的 order parameters 和 超導電流。並由上述這兩個物理量來描述層狀二類超導體在磁場下(大於Hc1)所形成的vortex 晶格結構。Vortex 晶格結構在乾淨超導體上有六角型的 對稱性，然而當有外加電場進入超導體後，vortex 的晶格結構就會有微小的形變。另外所計算出的I-V 曲線可以符合理論解析的結果。最近幾年具有奈米尺度的pinning 陣列的超導體被制做出來並且受到注意，其中具有Abrikosov 晶格對稱性的pinning 陣列最 備感興趣。由模擬計算出的動態order parameter 可以看到在具有pinning 陣列的超導體中的vortex 流是由interstitial vortex 所構成。而I-V 曲線也會受到pinning 陣列的影響，因為vortices 會陷在pinning centers 上而無法移動(如果pinning force 小於 driving force)，如此一來由vortex 移動所產生的能量損耗就可以減少。

Static and dynamic distributions of the superconducting condensate order parameter and current density is studied by numerical simulation of the 2D time-dependent Ginzburg-Landau equations. They describe the vortex lattice in layered type II superconductors under magnetic fields above the lower critical field. In a clean superconductor the non-linear J-E characteristics were calculated and compared to existing analytic results. The Abrikosov lattice which is hexagonal in statics is deformed due to the electric field. The artificial pinning arrays on the nano scale were fabricated recently and are investigated for the most interesting case of the pinning superlattice commensurate with the Abrikosov lattice. The dynamical order parameter distribution shows that the vortex transport (flux flow) is conducted via diffusive motion of the so called interstitial vortices. The J-E characteristics are strongly influenced by the pinning, since the vortices are trapped on the pinning centers and thus the energy dissipation (Joule heat) inside the cores of the moving vortices is reduced.