TDGL Simulation on Angular Dependence of Critical Current Density in Superconductors with Columnar Defects

Abstract

We numerically solved the three dimensional time-dependent Ginzburg-Landau (TDGL) equations to visualize the motion of the quantized magnetic flux lines in the superconductor under the transverse magnetic field B. We investigated the angular dependence of the critical current density Jc in the columnar pins using TDGL equations. As a result of simulations, it was confirmed that Jc decreases as increasing the angle θ between the columnar pins and the quantized magnetic flux lines. In particular at B = 0.4, Jc sharply decreased at θ between 20° and 30°. This result was compared with the calculation result of the overlapped volume between the quantized magnetic flux and the pins. The calculated result by TDGL equations was in good agreement with the calculated result by the overlapped volume. In addition, Jc was calculated using various pins such as the sphere, the columnar and the plane pins. It was found that plane pins are more effective than pins of other shapes. In addition, although it is experimentally difficult to fabricate, Jc of the star-shaped pin was obtained by the TDGL simulations. It was found that the Jc of the star-shaped pin shows the highest performance among all the kinds of configurations for the columnar pins in high magnetic fields.