Vortex state of layered superconductors probed by Josephson plasma resonance

约瑟夫森等离子体共振是探测层状超导体涡旋态的有力手段，使我们能够定量地确定层间约瑟夫森耦合。在本研究项目中，我们测量了高度各向异性的Bi2Sr2CaCu2O8&gt；8中涡旋晶格熔入液体中时约瑟夫森耦合的变化。结果表明，当穿过熔线时，约瑟夫森耦合强度发生了很大的变化。这一结果表明，涡旋晶格经历了从三维晶格到去耦合薄饼气的转变。我们还研究了重离子辐照的影响。结果表明，柱状缺陷的引入极大地改变了约瑟夫森耦合。解耦的煎饼与磁场耦合的耦合转变。这种转变几乎发生在匹配场的三分之一。通过对共振的详细分析，我们定量地计算了沿c轴方向的针尖的相关长度。

Josephson plasma resonance is a powerful means to probe the vortex state of layered superconductors, enabling us to determine the interlayer Josephson coupling quantitatively. In this research projest, we have measured how the Josephson coupling changes when the vortex lattice melts into the liquid in highly anisotropic Bi_2Sr_2CaCu_2O_<8+8>. We showed that the Josephson coupling strength changes dramatically when going accross the melting line. This result shows that the vortex lattice undergoes the transition from the three dimentional lattice to the decoupled pancake gas. We also studied the effect of the heavy-ion-irradiation. We showed that the introduction of the columnar defects changes the Josephson coupling dramatically. The coupling transition in which the decoupled pancakes couple with magnetic field. This transition occurs almost one-third of the matching field. We calculated the correlation length of the pancekes along the c-axis quantitatively from the detailed analysis of the resonance.