磁通格子的有序-无序相变和反向熔化

Order-disorder transitions and inverse melting in vortex lattices

考虑了无序钉扎、热涨落和磁通互作用 ,用MonteCarlo分子动力学模拟方法研究二维磁通格子在无序钉扎强度和温度空间的相图 ,以及由布拉格玻璃相到非晶磁通玻璃相和到磁通液体相的有序 无序相变 .为了决定磁通格子的序 ,计算了静态结构因子和磁通格子位形的有限尺寸指数 .计算结果表明 ,Bragg玻璃相在低温的无序磁通玻璃相和高温的磁通液体相之间 ,表现出磁通格子的反向熔化行为 .分析后认为 ,这一反向熔化行为起因于磁通之间互作用的温度效应 .

Using Monte Carlo molecular dynamics simulation for a two-dimensional vortex lattice with random pinning, thermal fluctuations and vortex-vortex interactions, we study the order-disorder transition from a Bragg glass to an amorphous vortex glass or a vortex liquid in the pinning strength-temperature phase diagram. In order to determine the order in the vortex lattice, we calculate the static structure factor and evaluate the finite size exponent from the configurations of the vortex lattice. It is found that the Bragg glass region is sandwiched in between the disordered vortex glass phase at lower temperatures and the vortex liquid phase at higher temperatures, exhibiting inverse melting behavior. We attribute the unusual inverse melting behavior to the temperature dependence of the vortex-vortex interactions.