S-wave symmetry

Then, from fig.lc it is seen that SC transition onset points Tconset(H)(= Tk(H)) are at the Bloch-Gruneisen curve (dashed curve). On the other hand, such a picture is characteristic for low temperature superconductors described by s-wave BCS theory. From this analogy it may be concluded that in the cuprates the SC order parameter is of s-wave symmetry, also. Moreover, as seen from magnetic phase H-T diagram, the... 

Hc2(T)-dependence (formed from SC transition onset points ( shoulder points)) is linear in T near Tc (H = 0), which fact is also characteristic for s-wave BCS and GL theory. Note that such a conclusion about s-wave symmetry of the SC order parameter was supported by a new phase-sensitive test of the order parameter symmetry on the Bi2Sr2CaCuOH+g bicrystal c-axis twist Josephson junction, the experiment [10] which is considered the strongest one up to date. 

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. 

Highly symmetric tips, ideally with s-wave symmetry for its electronic structure at the Fermi level. 

The residual absorption found in the vast majority of cuprates is not consistent with s-wave symmetry of the superconducting order parameter. Since the DOS inside the gap region of an s-wave superconductor is exactly zero at T = 0, the dissipative part of the conductivity must vanish for a) < 2A, in clear contrast with the experimental data. There have been several attempts to explain the residual absorption in the superconducting state assuming d-wave symmetry. In a d-wave superconductor, the DOS is finite at all finite... 

Above all, an order parameter other than s-wave symmetry has been argued for intensively in order to explain the experimental results from, e.g., NMR, penetration depth, speeifie heat, neutron scattering, and phase-sensitive SQUID measurements. Up to now, it seems that the argument has been converging to consider that the symmetry of the order parameter in these materials essentially has d-wave symmetry. 

Once the specimen turns to a superconducting state, the obtained superconductor-insulator-normal metal (SIN) spectrum probes the quasiparticle excitation in the superconductor, which directly reflects the symmetry of the order parameter A(k). If A(k) has simple s-wave symmetry, as is realized in conventional low-temperature superconductors, one expects a finite gap of A with overshooting peaks just outside the gap in N(E), as illustrated in fig. 6. Even if A(k) possesses anisotropic s-wave symmetry, a finite gap, corresponding to the minimum gap, appears. In dx2-yi superconductors with A(k) = coslkx - cos 2, in contrast, N(E) is gapless with linear N(E) for E A. It is noted that the extended-s wave A(x) = cos 2kx + cos 2ky is also characterized to possess a gapless feature with two singularities bX E = A and A2. 

The details of the superconducting gap structure form a rich source of information about the pairing mechanism. If the pairing is of typical s-wave symmetry, a finite gap is... 

On the other hand, microwave penetration depth (Anlage et al. 1994) and Raman spectroscopy measurements (Stadloper et al. 1995) on the electron-doped superconductor Ndi 85Ceo.i5Cu04-, indicate that the superconducting order parameter of this material has s-wave symmetry. 

Symmetry of superconducting state. No Hebel-Slichter coherence peak was observed in either k -(ET)2Cu(NCS)2 or c-(ET)2Cu[N(CN)2]Br in NMR measurements, ruling out a BCS s-wave state. The symmetry of the superconducting state of c-(ET)2Cu(NCS)2 had been controversially described as normal BCS-type or non-BCS type however, scanning tunneling spectroscopy showed f-wave symmetry with line nodes along the direction near ti/4 from k - and Kc-axes [228, 229], and thermal conductivity measurements were consistent with this result [230]. c-(ET)2Cu [N(CN)2]Br showed the same symmetry [231]. 

Similar to the. y-wave model, the Na-atom-tip model predicts a poor resolution. The agreement of the Na-atom-tip model with the y-wave-tip model does not mean that the s-wave-tip model describes the actual experimental condition in STM. According to the analysis of Tersoff and Lang (1990), real tips are neither Na or Ca, but rather transition metals, probably contaminated with atoms from the surface (for example. Si and C are common sample materials). For a Si-atom tip, the p state dominates the Fermi-level LDOS of the tip. For a Mo-atom tip, while the p contribution is reduced, this is more than compensated by the large contribution from states of d like symmetry. The STM images from a Si, C, or Mo tip, as predicted by Tersoff and... 

See Surface states Tersoff-Hamann approximation See s-wave-tip model Tetragonal symmetry 128 Tip annealing 286, 288 Tip preparation 281—285 cutting 282... 

Then, note also that recently it was introduced a concept of so-called hidden order in the cuprates (see, e.g. [16]). Such an order is attributed to d-density wave (DDW) order. However, in their statement the type of this DDW order is not concrete but it is only considered as competing (not vital) order for SC one, moreover it is considered as corresponding to the superconductivity with dx2 yi -wave pairing symmetry. As follows from above this concept may be described in terms of the (spin) density wave (S) (DW) with a dx2 y2 -wave symmetry accompanied by (charge) density wave (C)... 

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