高温超导体磁通钉扎和磁通动力学研究简介

ψ=ψ0eiφ行为用统一的波函数进行描述,其相位φ在宏观尺度上是相同的.当磁场低于一定值的时候,在超Φ0=h/2e保证最大的界面面积,降低系统能量.该最小的磁通束被称为磁通量子,其磁通量是(h为普朗克超导态是一个宏观量子相干态,其载流子是库珀对.在没有外加磁场和电流的时候,这些库珀对的运动导体的边界处穿透深度内会出现一...

Brief introduction to flux pinning and vortex dynamics in high temperature superconductors

Superconductivity is achieved through macroscopic phase coherence;the charge carriers are Cooper pairs.In absence of an external magnetic field and applied current, the behavior of these Cooper pairs can bedescribed by a single wave function ψ=ψ0e^iφ, and the phase is uniform over the space. When applying anexternal field but still below a certain threshold, a screening current will be established at the surface, whichprohibits the entering of magnetic field, that is so-called Meissner effect. When the external field is larger thanthis threshold, the magnetic flux will penetrate into the sample, forming the interface of superconducting andnormal state regions. According to the sign of this interface energy, we can categorize superconductors intotype-Ⅰ (positive interface energy) and type-Ⅱ (negative interface energy). Most superconductors found so far aretype-Ⅱ in nature. Due to the negative interface energy in type-Ⅱ superconductors, the penetrated magnetic fluxwill separate into the smallest bundle, namely the quantum flux line, with a quantized flux Ф0=h/2e(h is thePlanck constant and e is the charge of an electron). There are weak repulsive interactions among these vortices,thus usually they will form a lattice, called mixed state. When applying a current, a Lorentz force will exert onthe flux lines (vortices) and will make them to move, this will induce energy dissipation and the appreciablefeature of zero resistance of a superconductor will be lost. By introducing some defects, impurities ordislocations into the system, it is possible to pin down these vortices and restore the state of zero resistance.The study concerning vortex pinning and dynamics is very important, which helps not only the understandingof fundamental physics, but also to the high power application of type-Ⅱ superconductors. This paper gives abrief introduction to the vortex dynamics of type-Ⅱ superconductors.