Theory of BSCCO Bicrystal C-Axis Twist Josephson Junctions: A New Phase-Sensitive Test of Order Parameter Symmetry

Abstract

There is still considerable interest in the orbital symmetry of the superconducting order parameter (OP) in the high temperature superconducting cuprates. Although there are many experiments that suggest the possibility of line nodes of the OP, most of these experiments are not sensitive to the phase of the OP. The important question for the determining whether a new type of pairing mechanism is really necessary is to decide if the OP really is odd under reflection about some mirror plane. In Bi₂Sr₂CaCu₂O_8+ð (BSCCO), there is only one mirror plane, the bc plane. There are thus two classes of OP’s: those that are even and odd, respectively, under reflections in this mirror plane. Generally s-wave OP forms are even, and d_x2-y2-wave forms are odd. [1] Thus, these two forms are completely incompatible with each other, so that near to T_c, only one of them can exist. Thus, it is most sensitive to test for the symmetry of the OP near to T_c.