高溫超導體中之渦流晶格加入雜質與熱擾之影響

Abstract

本論文建立在Ginzburg-Landau 理論的基礎之上, 計算在高溫超導體中加入雜質與熱擾如何影響渦流晶格之自由能密度變化. 我們首次開發以微擾的方法計算加入雜質之渦流晶格自由能密度, 然後以非微擾的方法計算加入熱擾之影響. 分別探討二維與三維系統, 並討論其對磁化率及融化線之影響.

Based on Ginzburg-Landau theory, we discuss the disorder and thermal fluctuation effects in vortex lattice of high Tc superconductors. Recently new experimental techniques (irradiation by various particles) allowed for quantitatively study of disorder effects. Thermal fluctuations are very important in high Tc superconductors and may cause for example melting of vortex lattices. Disorder effects very prominent in transport in addition change thermodynamical properties like magnetization and shift the melting line down. We calculate for the first time the free energy density with disorder and thermal fluctuations of the vortex lattice separatly in 2D and 3D in the region not far from the Hc2 line. We developed a perturbative method in the framework of Ginzburg-Landau approach to calculate the free energy in the presence of the disorder field. Then other thermodynamical quantities like magnetization are calculated. To consider thermal fluctuations we applied a nonperturbative replica trick previously widely used in disordered electronic systems and spin glasses.