D-wave order parameter

Key words Bi2Sr2CaCu208+x c-axis Transport and Magneto-transport, Single Crystal Whiskers, d-wave, Order Parameter Symmetry, Josephson Flux-flow Resistivity. 

IV. 2 Evidence for d-Wave Order Parameter Symmetry in Bi-2212 from Experiments on Interlayer Tunneling... 

Where for example for the d-wave order parameter with /(k) = cos(2 >) and two orthogonal line nodes parallel to c one has for planar magnetic field (Won and Maki, 2000)... 

The change from the second-order nature of the transition observed at zero and low magnetic field to first order at high fields occurs at To 1.1 K = 0.48rc. This value should be compared with the estimate of 0.33 deduced from the Chandrasekhar-Clogston field of a d-wave order parameter and the orbital critical field obtained from extrapolating the behavior close to the zero-field transition to low temperatures. 

The I—V characteristic calculated based on a d-wave order parameter. 

The reported superconducting gap spectra have been analyzed in the fiamework of d-wave superconductivity. It has been found that results can be, in principle, described in terms of the d-wave order parameter. 

If a conventional superconductor (S) described by a s-wave order parameter symmetry (OPS) is put together with a non conventional superconductor (D), described by a pure d-wave OPS, to form two junctions in a superconducting loop, as indicated in Fig. 4, a self 7r — frustrated loop is achieved [van Harlingen 1995], Indeed, one of the two SD junctions behaves as a conventional "0" junction, since the Josephson coupling is between the positive lobe of the d-wave superconductor (white color in Fig. 4) and the S electrode on the contrary, the other junction is a V junction, because the coupling is now between the S electrode and the negative lobe. As a consequence, a shift of 7r along the loop is achieved and the device is self-frustrated by a half flux quantum. 

Fig. 1 Solid-state NMR structure analysis relies on the 19F-labelled peptides being uniformly embedded in a macroscopically oriented membrane sample, (a) The angle (0) of the 19F-labelled group (e.g. a CF3-moiety) on the peptide backbone (shown here as a cylinder) relative to the static magnetic field is directly reflected in the NMR parameter measured (e.g. DD, see Fig. 2c). (b) The value of the experimental NMR parameter varies along the peptide sequence with a periodicity that is characteristic for distinct peptide conformations, (c) From such wave plot the alignment of the peptide with respect to the lipid bilayer normal (n) can then be evaluated in terms of its tilt angle (x) and azimuthal rotation (p). Whole-body wobbling can be described by an order parameter, S rtlo. (d) The combined data from several individual 19F-labelled peptide analogues thus yields a 3D structural model of the peptide and how it is oriented in the lipid bilayer...

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... 

It should be noted here that the conclusion about s-wave nature of the SC order parameter is consistent with conclusion about s-wave symmetry of the SC order parameter in the bulk and d-wave symmetry at the surface of the sample of the cuprates [17]. It was noted in [17] that most conclusions about d-wave symmetry was obtained in experiments (e.g. ARPES ones) on the cuprates in which mainly surface phenomena have been used. In this sense, the resistive measurements on the cuprates (see, e.g. [4]) are essentially bulk in the nature. In addition, the electron scattering (in resistivity measurements) is sensitive to the spin disorder in the system (magnetic contribution in the electrical resistivity appears, see Sec.l). Moreover, the electron scattering permits probe not only static magnetic order but dynamical (short-lived) ones because of short characteristic times as compared e.g. with usual neutron scattering. 

In this paper, we concentrate on the /j+SR measurements and determine if YBa2Cu307 is a bulk. v-wave (nodeless) superconductor, as determined in Refs. 1-3, or a d-wave superconductor, whose order parameter A(k), changes sign as a function of k, as claimed in Ref. 8. In making this determination, we show that the features observed in the single-crystal data of Ref. 8 are actually due to temperature-activated fluxon de-pinning, an effect which is not readily observable in strongly pinned systems such as the early powder samples or the early heavily-twinned crystals. 

Experiments utilizing microwave cavity resonance, uc susceptibility, or rf resonance12 have been executed on YBa2Cu307 to test theoretical predictions of d-wave pairing theory for the non-linear Meissner effect.13 The predicted effects turned out to be either absent or unobservably small. Moreover, the predicted four-fold symmetry in the ab plane for the d(.x2 — y2 ) order parameter is also absent.14... 

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