dc Josephson current for d-wave superconductors with charge density waves

Abstract

dc Josephson tunnel current Ic between a dx2−y2-wave superconductor and charge density waves (CDWs)—e.g. a high-Tc oxide and a conventional isotropic superconductor—was considered theoretically. Directionality of tunneling was taken into account. It was found that the dependence of Ic on the angle γ between the direction of the superconducting lobe and the plane normal to the junction is significantly altered by CDWs. For certain doping levels it may be nonmonotonic, as can be readily determined experimentally. For comparison, presented here are the corresponding results obtained for the tunnel junction between CDWs in an s-superconductor and a conventional isotropic superconductor.

Anomalous temperature dependence of the stationary Josephson tunnel current in junctions between d-wave superconductors

“…Hereafter, we excluded from consideration an important ingredient of pseudogapping, which is present at almost all dopings [58,59], to study Josephson tunneling between dwave superconductors just as it is. Tunnel directionality plays one of the key roles in the proposed theory.…”

“…Therefore, when integrating over the FS, we include a certain FS section described by the angle θ and, inevitably, a section described by the angle ( /2), θ ± π for which the corresponding values of the order parameter "profile function" ( ) Those terms can be factorized into cos , θ where θ is the angle at which the pair/quasiparticle transmits through the barrier, and a factor that can be incorporated into the junction normal-state resistance N R [20,[64][65][66][67][68]. Second, the tunnel matrix elements T pq  in (2) become momentumdependent [25,[31][32][33][34][35][36][37][38]58,59,69]. In the case of isotropic superconductors (the corresponding function ( ) = 1), f ∆ θ all gap-dependent multipliers can be taken outside the integral over ;…”

“…T → Both kinds of curves are really observed, and this qualitative agreement between the theory and the experiment may testify that (i) the midgap states in cuprate junctions are effectively wiped out by the diffusive scattering, so that the problem of Andreev scattering may be of academic interest for actual boundaries, or (ii) the superconducting order parameter includes such a subdominant component [54,57] that the nodes in the overall superconducting energy gap are absent. We note that wide enough pseudogaps (being most probably, of charge-or spindensity-wave origin) can also, in principle, occupy the node areas, thus affecting the angular and temperature dependences of Josephson current [58,59].…”

Stationary Josephson current as a tool to detect charge density waves in high-Tc oxides

“…For any of those materials and especially for cuprates, it seems important to propose such experimental studies of superconducting properties, which would demonstrate manifestations of CDW existence, although the CDW gapping is an insulating rather than a superconducting one. In a number of publications, we suggested that certain measurements of the stationary Josephson critical current, I c , between quasi-two-dimensional CDW superconductors with the d x 2 Ày 2 order parameter symmetry (probably inherent to cuprates with the reservations discussed above) can conspicuously reveal such dependences that would reflect CDW gapping as well or at least demonstrate that the actual gapping character differs from the pure d x 2 Ày 2 one [60,[87][88][89][90]. In particular, we considered in detail [89] the angular dependences of I c , i.e.…”

dc Josephson Current Between an Isotropic and a d-Wave or Extended s-Wave Partially Gapped Charge Density Wave Superconductor

“…It should concern Josephson currents phenomenon too [129][130][131][132][133][134], although this topic has not been properly developed so far.…”