Angular dependence of the Josephson critical current in c-axis twist junctions of high-temperature superconductors

Abstract

We have investigated theoretically the case of a highly anisotropic layered superconductor consisting of two identical parts that are twisted with respect to each other by an angle φ0 about the c axis. This work was motivated by recent high-quality c-axis twist Josephson junctions prepared with Bi2Sr2CaCu2O8+δ by Li et al. Our interest lies in studying whether the Josephson critical voltage IcRn measured along the c axis in high-temperature superconductors as a function of φ0 could give valuable information regarding the orbital symmetry of the superconducting order parameter. We assume both coherent and incoherent interlayer tunneling processes, and ordinary intralayer impurity scattering. We have derived and studied the effective Lawrence-Doniach model appropriate for the cases of pure s-wave and dx2−y2-wave order parameters, a dominant dx2−y2 and subdominant dxy mixed order parameter, and a dominant dx2−y2 with a subdominant s-wave mixed order parameter. Our results suggest that Josephson tunneling across the c-axis twist junctions can indeed be a useful tool for probing the superconducting order-parameter symmetry. Further experiments to clarify the situation are suggested.

Source-reported materials — not catalogue approval

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