層狀二類超導體在強磁場的溫度-雜質相圖

Abstract

在本論文中，我們使用二維金斯堡－朗道模型及準動量基底來模擬二維第二類超導體，並由蒙地卡羅方法來分析漩渦結構在熱擾和無序下的行為。我分析了在簡化溫度a_T=-17~-11和無序常數ζ=0~1下的相變行為。藉由觀察平均後的傅立葉轉換的漩渦分布去分辨系統的相。並藉由比較Y. Kato and N. Nagaosa的蒙地卡羅模擬，在純淨系統下有限大小樣品的熔點，找出切確漩渦固態和漩渦液態的分界線。再由比較同樣兩種不同雜質分布的樣品，因為在雜質夠大情況下漩渦會固定在雜質上，所以可以藉此切確找出玻璃態的轉換線。

The thermal fluctuations and disorder of vortices structure in highly anisotropic layered type II superconductors has been studied by Monte Carlo simulation in two dimensional Ginzburg-Landau model with the quasi-momentum basis. Vortices structure are studied with disorder parameter ζ=0~1 and reduced temperature a_T=-17~-11 in the thesis. I developed the rotation averaging to analysis the snapshots of the Fourier transform of the superfluid density. I identified the melting line with disorder by comparing the vortices structure in pure system that the melting point of finite sample has been developed by Y. Kato and N. Nagaosa. And I identified the glass (irreversibility) line by comparing the difference of vortices structure with two different distribution of disorder. One can see the vortices pin on the disorder with disorder strong enough so that there are difference between the vortices structure with two different distribution of disorder to find the glass transition line. I will give a a_T-ζ phase diagram in the end.