Time-reversal Symmetry Breaking State Research Articles

Proximity-induced time-reversal symmetry breaking at josephson jnctions betweend-wave superconductors

Based on a Ginzburg Landau (GL) theory, it is shown that under certain conditions a locally time-reversal symmetry breaking state can occur at Josephson junctions between unconventional, in particular,d-wave superconductors. Numerical solutions of the GL equations derived from thet-J model within a slave-boson mean-field approach show this effect for realistic choice of parameters. An experiment to test the relevance of this theory to High-Tc superconductors is proposed.

Ginzburg-Landau equations for a d-wave superconductor with applications to vortex structure and surface problems.

The properties of a {ital d}{sub {ital x}}{sup 2}{minus}{ital y}{sup 2}-wave superconductor in an external magnetic field are investigated on the basis of Gorkov`s theory of weakly coupled superconductors. The Ginzburg-Landau (GL) equations, which govern the spatial variations of the order parameter and the supercurrent, are microscopically derived. The single vortex structure and surface problems in such a superconductor are studied using these equations. It is shown that the {ital d}-wave vortex structure is very different from the conventional {ital s}-wave vortex: the {ital s}-wave and {ital d}-wave components, with the opposite winding numbers, are found to coexist in the region near the vortex core. The supercurrent and local magnetic field around the vortex are calculated. Far away from the vortex core, both of them exhibit a fourfold symmetry, in contrast to an {ital s}-wave superconductor. The surface problem in a {ital d}-wave superconductor is also studied by solving the GL equations. The total order parameter near the surface is always a {ital real} combination of {ital s}- and {ital d}-wave components, which means that the proximity effect cannot induce a time-reversal symmetry-breaking state at the surface.

Proximity-Induced Time-Reversal Symmetry Breaking at Josephson Junctions between Unconventional Superconductors

We argue that a locally time-reversal symmetry breaking state can occur at Josephson junctions between unconventional superconductors. Order parameters induced by the proximity effect can combine with the bulk order parameter to form such a state. This property is specifically due to the intrinsic phase structure of the pairing wave function in unconventional superconductors. Experimental consequences of this effect in high-temperature superconductors are examined.