Geometry of the junction between a conventional s-wave superconductor and a high-Tc dx2 − y2 - or s-superconductor partially gapped by charge density waves (CDWs, induced by dielectric, i.e., electron-hole, pairing). The angle α denotes the half-width of each of four angular sectors at the Fermi surface, where the CDW gap appears. The profiles of the CDW dilelectric (Σ), and s-wave (Δ s ) and d-wave (Δ d ) superconducting order parameters of the high-Tc superconductor are shown for the “parent” CDW metal and BCS d-superconductor. Δ* is the gap of the conventional superconductor; γ is the angle between the coincident bissectrices of the closest superconducting lobe (if any) and CDW-gapped sector, on the one hand, and the normal n to the junction plane, on the other hand. θ0 is the directional sector of effective tunneling in two models with step-like and graduate tunneling directionality (see explanations in the text).
Dependences of the dimensionless dc Josephson current ic on γ for the smooth (a) and stepwise (b) models of tunnel directionality at α = 15° and for various θ0. The zero-T values of the gaps are Σ(0) = 36.3 meV and Δ(0) = 28.3 meV, no matter the symmetry of the oxide superconducting order parameter; Δ*(0) = 1.4 meV (the specific gap values correspond to the experimental data for Bi2Sr2CaCu2O8+δ and Nb, respectively). Further explanations see in the text.
The same as in Fig. 2, but for θ0 = 15° and various α’s.
The dependences ic (α) for γ = 0 and θ0 = 15° for d- and s-symmetries of high-Tc oxide order parameter for the smooth (a) and stepwise (b) models of tunnel directionality.
The same as in Fig. 2, but for θ0 = 15° and various symmetries of the superconducting order parameter coexisting with the CDW order parameter (s and d curves) and for a dx2 − y 2 -wave superconductor without CDWs (pure d-SC curve).
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