| The discovery of high Tc superconductors has shattered the comforting sense of understanding that we had of the phase diagram and physical properties of typeⅡsuperconductors, and in particular of the mixed (vortex) phase in such systems, perfect triangular crystal (the Abrikosov the phase diagram has been the cornerstone of our understanding of all typeⅡsuperconductors for more than four decades).in high Tc, one could reach much higher temperatures, and it was soon apparent that some of the physics linked to the existence of the thermal fluctuations and disorder had been overlooked. This led to a burst of investigations, both theoretical and experimental, to understand the physical properties of such vortex matter. Of course, high Tc were not the only field of investigations and low Tc superconductors were reexamined as well。In Chapter 1,we firstly introduce the history of superconductors and some import event, methods in experiment such as Small angle neutron scattering, STM,and Bitter pattern technique.In Chapter2,we introduce some important idea of vortex matter. Elastic Description of Vortices, Disorder, Experimental Facts of Bragg Glass Theory and peak effect, Dynamics of Vortices.In Chapter 3.For the 0 temperature.The new dynamic phase diagram for driven vortices with varying lattice softness we present here indicates that, at high driving currents, at least two distinct dynamic phases of flux flow appeardepending on the vortex-vortex interaction strength. When the flux lattice is soft, the vortices flow in independently moving channels with smectic structure. For stiff flux lattices, adjacent channels become locked together, producing crystallinelike order in a coupled channel phase. At the crossover lattice softness between these phases, the system produces a maximum amount of voltage noise. Our results relate spatial order with transport and are in agreement with experiments. In Chapter 4,we perform 2D Langevin simulations and W-L algorithm.From the energy of the complex of pinning and vortex, considered the pinning centers can contain the number of vortexs.We find one pinning can contain two vortexs only at T/Tc>0.69.Meanwhile,we observe and report that the PE results from the transition from strong pinning to weak collective.In addition,the PE is a vortex phase transition but not a dynamical phenomenon. |
