Influence of d-Wave Symmetry on Irreversibility Line and Critical Current Densities

Abstract

The enhancement of the upper critical field, Bc2, in a low temperature and high magnetic field region has been proposed theoretically, due to the mixing of dx2-y2 - and dxy-symmetries for two-dimensional (2D) d-wave superconductors. Based on the Bc2 enhancement theory, the irreversibility field, Bi, and the critical current density, Jc, for high-Tc superconductors were calculated using the power law of Bi ∝Bc2n. It is found that both Bi and Jc for chemical vapor deposition (CVD)-processed YBa2Cu3O7 can be well interpreted by the present model. This fact suggests that the concave temperature dependences of Bi and Jc originate from Bc2 for 2D d-wave superconductors. Moreover, the qualitative temperature dependence of Bi for high-Tc superconductors changes slightly with the anisotropy but the value of Bi decreases drastically with increasing the anisotropic parameter γ2.