Key features for high-T c -superconductivity phenomenon: antiferromagnetic exchange as attractrive interaction and a saddle-point singularity close to Fermi level

1996 ◽  
Vol 105 (3-4) ◽  
pp. 597-602 ◽  
Author(s):  
F. Onufrieva ◽  
S. Petit ◽  
Y. Sidis
Keyword(s):  
Saddle Point ◽  
Fermi Level ◽  
Antiferromagnetic Exchange ◽  
Point Singularity ◽  
Key Features

Resonant Raman scattering at the saddle-point singularity inInxGa1−xAs

1985 ◽  
Vol 32 (2) ◽  
pp. 1005-1008 ◽  
Author(s):  
K. P. Jain ◽  
R. K. Soni ◽  
S. C. Abbi ◽  
M. Balkanski
Keyword(s):  
Raman Scattering ◽  
Saddle Point ◽  
Point Singularity ◽  
Resonant Raman ◽  
Resonant Raman Scattering

scholarly journals An experimental investigation of meniscus roll coating

1998 ◽  
Vol 355 ◽  
pp. 17-44 ◽  
Author(s):  
P. H. GASKELL ◽  
G. E. INNES ◽  
M. D. SAVAGE
Keyword(s):  
Saddle Point ◽  
Flow Rate ◽  
Pressure Profile ◽  
Critical Flow ◽  
Flow Rates ◽  
Roll Coating ◽  
Primary Fluid ◽  
Secondary Transfer ◽  
Key Features ◽  
Fluid Transfer

A two-roll apparatus is used to explore experimentally the detailed fluid mechanics of meniscus roll coating in which inlets are starved and flow rates are small. Both forward and reverse modes of operation (with contra- and co-rotating rolls) are investigated using optical sectioning combined with dye injection and particle imaging techniques. That part of parameter space where meniscus coating occurs is identified by varying the roll separation and roll speeds and hence flow rate and capillary number.Key features of the flow structures identified in the forward mode include two large eddies (each with saddle point, separatrix and sub-eddies), a primary fluid transfer jet and the existence of two critical flow rates associated with the switching-on of a second fluid transfer jet and the switching-off of the primary transfer jet followed by a change in the flow structure. In the reverse mode, the key features are a single large eddy consisting of two sub-eddies, a saddle point and separatrix, a primary fluid transfer jet and once again two critical flow rates. These correspond to (i) the switching-on of a secondary transfer jet and (ii) the disappearance of a saddle point at the nip resulting in the merger of the primary and secondary transfer jets.Measurements of film thickness and meniscus location made over a range of speed ratios and capillary numbers are compared with theoretical predictions. A plate–roll apparatus is used to confirm the presence, for very small flow rates, of a sub-ambient, almost linear, pressure profile across the bead. Investigated also is the transition from inlet-starved to fully flooded roll coating as flow rate is increased and the changes in flow structure and pressure profile are observed.

scholarly journals Topological phase diagram and saddle point singularity in a tunable topological crystalline insulator

2015 ◽  
Vol 92 (7) ◽  
Author(s):  
Madhab Neupane ◽  
Su-Yang Xu ◽  
R. Sankar ◽  
Q. Gibson ◽  
Y. J. Wang ◽  
...  
Keyword(s):  
Phase Diagram ◽  
Saddle Point ◽  
Topological Phase ◽  
Point Singularity ◽  
Topological Crystalline Insulator

Electromagnetic field of a dipole on a two‐layer earth

Geophysics ◽  
1981 ◽  
Vol 46 (3) ◽  
pp. 309-315 ◽  
Author(s):  
W. C. Chew ◽  
J. A. Kong
Keyword(s):  
Electromagnetic Field ◽  
Saddle Point ◽  
Branch Point ◽  
Asymptotic Approximation ◽  
Spherical Wave ◽  
Geometrical Optics ◽  
Parabolic Cylinder ◽  
Point Singularity ◽  
Image Source ◽  
Free Part

The electromagnetic field due to a horizontal electric dipole placed on top of a two‐layer earth is represented in terms of fields due to a dipole over a half‐space earth and its image source fields. Integral representations of image source fields are evaluated with uniform asymptotic approximations. Leading order ordinary saddle‐point approximation, giving rise to the geometrical optics approximation (GOA), is shown to be inaccurate. This is especially true when the angle of observation is close to the critical angle, which corresponds to the presence of a branch‐point singularity near the saddle point. In the uniform asymptotic approximation, the integrand of the image source integral is split into a branch‐point free part and another part containing the branch‐point singularity. The branch‐point free part can be approximated with a spherical wave function, while the part containing the branch point can be approximated with parabolic cylinder functions. Vertical magnetic field components and the horizontal electric field component near the surface are illustrated and compared with the geometrical optics approximation, giving the direct numerical result as well as experimental measurement. It is shown that the uniform asymptotic approximation yields excellent agreement with numerical and experimental results compared to the geometrical optics approximation.

Superconductivity in the Strong Coupling Limit: Van Hove Singularity and Extended Saddle Point Singularity Scenario

1997 ◽  
Vol 11 (07) ◽  
pp. 303-309
Author(s):  
Sujit Sarkar
Keyword(s):  
Saddle Point ◽  
Strong Coupling ◽  
Weak Coupling ◽  
Nearest Neighbor ◽  
Strong Coupling Limit ◽  
Dimensional System ◽  
Coupling Theory ◽  
Point Singularity ◽  
Van Hove Singularity ◽  
Weak Coupling Theory

The effect of orthorhombic distortion and second nearest neighbor hopping on the transition temperature (T c ) and the isotope-shift exponent (α) have been studied for a two dimensional system, within the framework of Eliashberg formalism in the van Hove singularity scenario. The behavior of T c and α have been discussed for the case of extended saddle point singularity. A comparison of the strong coupling theory results is made with the results of weak coupling theory. From our study it reveals that the effect of singularity in the density of states (DOS) in the strong coupling limit is not so significant as that in weak coupling case.

Observation of a Saddle-Point Singularity inBi2(Sr0.97Pr0.03)2CuO6+δand Its Implications for Normal and Superconducting State Properties

1994 ◽  
Vol 73 (24) ◽  
pp. 3298-3301 ◽  
Author(s):  
D. M. King ◽  
Z. -X. Shen ◽  
D. S. Dessau ◽  
D. S. Marshall ◽  
C. H. Park ◽  
...  
Keyword(s):  
Saddle Point ◽  
Superconducting State ◽  
Point Singularity
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