Search

On the basis of resistively-shunted junction dynamics, we study vortex dynamics in two-dimensional Josephson junction arrays with asymmetrically single and bimodulated periodic pinning potential for the full range of vortex density f. The ratchet effect occurring at a certain range of temperature, current, and f, is observed in our simulation. We explain the microscopic behavior behind this effect by analyzing the vortex distribution and interaction. The reversal of the ratchet effect can be observed at several f values for a small driven current. This effect is stronger when the asymmetric potential is simultaneously introduced in two directions.

In the framework of elastic theory, we study the vortex-lattice melting transitions in magnesium diboride for magnetic fields both parallel and perpendicular to the anisotropy axis. Using the parameters from experiments, the vortex-lattice melting lines in the H-T diagram are located systematically by various groups of Lindemann numbers and the anisotropic parameters. It is observed that the theoretical result for the vortex melting with parallel and perpendicular fields agrees well with the experimental data., Comment: 4 pages, 4 figures

The depinning phase transition of the Mullins–Herring equation with an external driving force and quenched random noise is studied in a short-time dynamic scaling scheme. Besides the critical driving force, all the critical exponents can be accessed, agreeing well with those in long-time steady-state simulations. The finite size effects on the critical exponents are also discussed. It is found that reasonable results can be achieved with a relatively small system, which highlights the advantage of the present approach.

The Ising-like phase transition of two-dimensional fully frustrated XY (FFXY) model with time dependent Ginzburg–Landau (TDGL) dynamics is studied by using the short-time dynamics scaling analysis. The transition temperature T c and the dynamic and static critical exponents z, 2 β / ν , and ν are estimated and are compared with the results of FFXY model under resistively-shunted junction dynamics (RSJ) and Monte Carlo (MC) dynamics. We find T c , z, and ν are roughly independent of dynamic mode but 2 β / ν is dependent on the dynamic mode.