Nodes, line

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]. 

FIGURE 20 Angle-dependent c-axis thermal conductivity of YNi2B2C (upper panel), 0 and 0 are defined in the inset. The lower pair of panels shows the gap symmetry in the case of (a) point nodes ((s + g) wave) and (b) line nodes and, additionally, the resulting angular variation of a quantity Izz, related to its value for 0 = 45°, that is proportional to the c-axis component of k (reprinted figures with permission from Izawa, K., Kamata, K., Nakajima, Y., Matsuda, Y., Watanabe, T., Nohara, M., Takagi, H., Thalmeier, P., Maki K., Phys. Rev. Lett. 2002,89,137006). 

Because of the limited dimensionality and anisotropy of the systems, the symmetry of SC order parameters is not always the same as that of BCS but can be anisotropic with line nodes [92]. 

Figure 12.1 The standing waves of a vibrating string. The fundamental (first harmonic) has no nodes the second harmonic is half the wavelength and twice the frequency of the fundamental and has one node, shown by a dotted vertical line. Nodes increase as firequency and energy increase.

The temperature dependence of Ks at low temperatures is exponential for s-wave pairing. In the case of a d-wave with a line-node gap, the temperature dependence of Ks at low temperatures is linear. Evv ocxvv does not change even below Tc. 

Ti has no coherence peak, followed by a sharp decrease below Tc. The large linear part, associated with the pair-breaking effect due to the imperfection of the crystal, is seen in the lower- Tc crystals. The relation between Tc and Nres agrees well with the theory as shown in Fig. 18 where To = 1.5 K is adopted, consistent with the present high-T crystals. In high-T( crystals, the T3 behaviour has been observed below 1 K down to 0.15 K, which implies the formation of the line-node gap. The 1 jT behaviour can be well interpreted by the line-node-gap model A([Pg.136]

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)... 

For 0.04 < T < 100 K, the SLR showed a strong T-dependence, indicating that the compound was much more itinerant than previously known Ce-based HF compounds. The observed T-variation was considered to indicate anisotropic spin fluctuations near a magnetic ordering, arising from a layered crystal structure. Bulk superconductivity set in at 0.40 K, below which there was no coherence peak and the SLR followed a relationship, suggesting unconventional superconductivity with an anisotropic (line-node) energy gap. 

Recently, much attention has been paid to the so-called anisotropic gap state superconductor. At T = 0, Cs(0)/yT<- exhibits (T/T ) temperature dependence in the case of gap function with point node, while (T/T<-) temperature dependence is observed in the case of gap function with line node. As low-energy excitation is possible, one can observe the power law T dependence at the low temperature in specific heat for p and d wave superconductors. The measurements of specific heat give extremely fruitful information about the superconducting gap complementary with other measurements, such as NMR. Even if a superconductor is not bulk, zero resistance may be observed when there is a continuous superconducting current path inside the sample. By using specific heat measurements, it is possible to determine whether superconducting behavior occurs in the bulk or not. We note that it is extremely important to check the bulk nature of pressure-induced SC by specific heat measurements imder pressure. 

Design Lines Nodes Graphs Calls Size... 

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