Percolative nature of current transport in polycrystalline MgB2 wires

The percolation model, taking into account the percolative nature of current transport due to anisotropy, is a powerful tool for predicting the field and temperature dependences of critical current in MgB2 superconducting wires. The critical current behaviour measured from MgB2 wires can be obviously explained by only four fitting parameters, the anisotropy parameter, the pinning force maximum, the upper critical field along the ab-plane, and the percolation threshold. Moreover, the temperature dependence of the upper critical field is further explained by the dirty-limit two-gap theory.