Vortex Pinning And Ratchet Effect In Two-Dimensional Josephson Junction Arrays

In this thesis, the vortex distribution in the different pinning potential in the two dimensional Josephson junction arrays is studied by numerical simulations with the use of the resistivity shunted junction dynamics.First, we briefly introduce the XY model and its dynamics, and the properties of vortex pinning. Based on this model, we construct different pinning arrays in the XY model. By the simulating the vortex distribution in the two-dimensional josephson junction arrays with triangular pinning potential, we clarify the efficient pinning effect of these pinning centers. Then by numerical measurement of the current-voltage characteristic, we found that the resistivity decreases with the pinning strength.We introduce the Ratchet effect in various physics systems in detail, including its generation process, generation condition, various ratchet effect, and its realization in superconductors. We study the ratchet effect in the two-dimensional josephson junction arrays with periodic but asymmetrical triangular pinning potential. It is found that, if applying the external current along oppositive derections to this system, because the current drives the vortex moving along different gradient of the pinning potential, there is a one-way conducting property in the IV-characteristics, similar to the diode rectification.