Superconducting order parameter

Keywords color superconductivity, order parameter, temperature, fluctuations... 

More than 15 years studies of high temperature superconductivity in cuprates accumulated many evidences of the d-wave type symmetry of the superconducting order parameter (OP) in these materials. The most strong ones has been found from the ARPES experiments [1], quantum interference... 

Abstract The combined bicrystal, artificial cross-whisker, and natural cross-whisker c-axis twist experiments on Bi2Sr2CaCu20s+a (Bi2212) provide strong evidence that the superconducting order parameter is predominantly s wave for T < Tc, and that the c-axis tunneling is strongly incoherent. 

Figure 1. The calculated variation of the parameter A0 in the wavefunction Eq. (1) and the calculated magnitude of the superconducting order parameter with x adapted from Ref. (2)...

Abstract In strong-coupling superconductors with a short electron mean free path the self-energy effects in the superconducting order parameter play a major role in the phonon manifestation of the point-contact spectra at above-gap energies. We compare the expressions for the nonlinear conductivity of tunnel, ballistic, and diffusive point-contacts and show that these expression are similar and correspond to the measurements of the phonon structure in the point-contact spectra for the 7r-band of MgB2. 

In the above mentioned formulae A (e) is the complex superconducting order parameter... 

The role of the grain boundary plane needs to be established, especially in view of anisotropic superconducting order parameters. In thin films, considerably smaller grain boundary junctions than those used in our work would be feasible and it should thus be possible to prepare samples with reasonably well defined facets. Of course, at inclinations such as for the 45°/[001] grain boundaries, where asymmetric facets dominate supposedly because of their much lower energy than other inclinations (see Fig. 10.4), symmetric facets may not form, at least not exclusively. Whenever there is coexistence of... 

Fig. 11.13. Experimental observations of (T = 4.2 K) as a function of misorientation angle from the results of several groups [11.1-11.3] show an exponential dependence. Where the results were reported at E = 77 K, the values at 4.2 K were extrapolated from the temperature dependence of Jq [11.45]. The grain boundary tunneling current calculated from eq. 11.2 using the grain boundary widths from Fig. 11.12 shows excellent quantitative agreement for a width defined by a copper(I) valence between 1.5 and 1.9. This copper valence corresponds to the copper(I) valence in bulk YBCO when it becomes non-superconducting. The predicted drop in due to the symmetry of the superconducting order parameter is insufficient by two orders of magnitude to account for the observed behavior.

In this work we apply anisotropic Glnzburg-Landau (GL) theory [22], previously extended by us to include coupled s-wave and d-wave superconducting order parameters [23], to qualitatively analyze the single-crystal and oriented-film data on the 214- and 123-materials. In particular we think that the large.Sommerfeld coefficients 7 - S mJ/mol [4,24,25] and 9 mj/mol [18,20] for the 40 K and 90 K... 

Figure 1. Schematic temperature dependence of the superconducting order parameters, where L Is for the mixed (s+d)-state and for the pure d j T - a -...

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