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

Abstract

The enhancement of the upper critical field, B c 2 , in a low temperature and high magnetic field region has been proposed theoretically, due to the mixing of d x 2 - y 2 - and d x y -symmetries for two-dimensional (2D) d-wave superconductors. Based on the B c 2 enhancement theory, the irreversibility field, B i , and the critical current density, J c , for high- T c superconductors were calculated using the power law of B i ∝ B c 2 n . It is found that both B i and J c for chemical vapor deposition (CVD)-processed YBa 2 Cu 3 O 7 can be well interpreted by the present model. This fact suggests that the concave temperature dependences of B i and J c originate from B c 2 for 2D d-wave superconductors. Moreover, the qualitative temperature dependence of B i for high- T c superconductors changes slightly with the anisotropy but the value of B i decreases drastically with increasing the anisotropic parameter γ 2 .