RELATIONSHIP BETWEEN THE FERMI SURFACE AND  THE SYMMETRY OF THE GAP FUNCTION IN UNCONVENTIONAL SUPERCONDUCTORS

The relationship between the Fermi surface (FS) and the symmetry of the gap function in unconventional superconductors is argued. It is found that the shapes of the FS are indeed related to the symmetry of the superconducting gap function, and is also influenced by the next nearest-neighbor overlapping. The application of the arguments to cuprate superconductors is briefly discussed. There is observed an interesting property that Luttinger's theorem perfectly holds for various pure gap symmetries in the weak-coupling limit while it is violated for dx2 - y2- and dx2 - y2 + idxy-wave symmetries in a few cases.

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ENERGY BAND OVERLAPPING IN HIGH-Tc SUPERCONDUCTORS

Modern Physics Letters B ◽

10.1142/s0217984996001681 ◽

1996 ◽

Vol 10 (30) ◽

pp. 1483-1490 ◽

Cited By ~ 10

Author(s):

M. MORENO ◽

R. M. MÉNDEZ-MORENO ◽

M. A. ORTIZ ◽

S. OROZCO

Keyword(s):

Weak Coupling ◽

Cuprate Superconductors ◽

Weak Coupling Limit ◽

Band Model ◽

Coupling Constant ◽

High Tc Superconductors ◽

Energy Bands ◽

Effective Coupling ◽

High Tc ◽

Two Band Model

Multi-band superconductors are analyzed and the relevance of overlapping energy bands to the high-T c of these materials is studied. Within the BCS framework, a two band model with generalized Fermi surface topologies is developed. Values of the overlapped occupancy parameters for typical cuprate superconductors are obtained as a function of the ratio R and the effective coupling constant, λ, in the weak-coupling limit. The overlap scale is of the order or lower than the cutoff (Debye) energy. The typical behavior of the isotope effect is obtained. As these superconductors have transition temperatures above the phonon barrier, the results of this approach are important to the generic understanding of the high-T c superconducting mechanism.

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MERCURY-BASED SUPERCONDUCTORS WITH QUASI-NORMAL OCCUPANCY

Modern Physics Letters B ◽

10.1142/s0217984995001170 ◽

1995 ◽

Vol 09 (18) ◽

pp. 1175-1184

Author(s):

M. MORENO ◽

R.M. MÉNDEZ-MORENO ◽

S. OROZCO ◽

M.A. ORTÍZ

Keyword(s):

Transition Temperature ◽

Fermi Surface ◽

Weak Coupling ◽

Cuprate Superconductors ◽

Energy Gap ◽

Oxide Superconductors ◽

Coupling Constant ◽

Effective Coupling ◽

Small Energy ◽

Copper Oxide Superconductors

A model with anomalous occupancy is applied to Hg-based cuprate superconductors. The anomaly consists of a small energy gap near the Fermi surface, the scale of the gap anomaly is of order of the cutoff (v.g. Debye) energy. Values of the anomalous occupancy parameters for Hg-based superconductors are obtained for different values of the ratio R and the effective coupling constant, within the weak coupling. As these materials have the highest transition temperature known for layered copper-oxide superconductors, they serve as a new testing ground for various proposed models.

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Effect of Next-Nearest-Neighbor Electron Hopping on Superconducting Gap of Cuprate Superconductors

SPIN ◽

10.1142/s2010324719500164 ◽

2019 ◽

Vol 09 (03) ◽

pp. 1950016

Author(s):

Pratima Beura ◽

Kamal L. Mohanta

Keyword(s):

Cuprate Superconductors ◽

Nearest Neighbor ◽

Chemical Potential ◽

Coupling Parameter ◽

Pairing Symmetry ◽

Function Technique ◽

Superconducting Gap ◽

Temperature Dependent ◽

Electron Hopping ◽

Grid Points

We study here a single band Hamiltonian model to describe the effect of next-nearest-neighbor (NNN) electron hopping on superconducting gap in Cuprates. The Hamiltonian consists of nearest-neighbor (NN) and next-nearest-neighbor (NNN) electron hopping integrals between the copper sides. By taking d-wave pairing symmetry into account, BCS type superconducting interaction is studied. By applying Zubarev’s Green function technique, the total Hamiltonian is solved. From the correlation function, the temperature-dependent superconducting gap (SC) equation is derived and is computed self-consistently by using technique [Formula: see text] grid points of the electron momentum. By varying SC coupling, chemical potential, J-T coupling parameter and second-nearest-neighbor electron hopping integral, the evolution of the order parameter is investigated.

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Fermi Surface Topology and the Superconducting Gap Function inUPd2Al3: A Neutron Spin-Echo Study

Physical Review Letters ◽

10.1103/physrevlett.97.057002 ◽

2006 ◽

Vol 97 (5) ◽

Cited By ~ 8

Author(s):

E. Blackburn ◽

A. Hiess ◽

N. Bernhoeft ◽

M. C. Rheinstädter ◽

W. Häußler ◽

...

Keyword(s):

Fermi Surface ◽

Spin Echo ◽

Gap Function ◽

Surface Topology ◽

Neutron Spin ◽

Superconducting Gap ◽

Neutron Spin Echo ◽

Fermi Surface Topology

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Statistical mechanics of quantum one-dimensional damped harmonic oscillators: II

Canadian Journal of Physics ◽

10.1139/p87-104 ◽

1987 ◽

Vol 65 (7) ◽

pp. 715-718 ◽

Cited By ~ 1

Author(s):

O. N. Borges ◽

L. A. Amarante Ribeiro

Keyword(s):

Master Equation ◽

Weak Coupling ◽

Weak Coupling Limit ◽

Harmonic Oscillators ◽

Equation Approach ◽

One Dimensional ◽

Master Equation Approach ◽

The One ◽

The Relationship ◽

Damped Oscillator

We show that the Caldirola–Kanai Hamiltonian of the one-dimensional damped oscillator describes in a specified basis a Gaussian, Markoffian process, in the weak coupling limit. We also discuss which assumption makes the process stationary and clarify the relationship with the master-equation approach.

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A WEAK COUPLING THEORY FOR La2CuO4: ln2–PARQUET APPROACH

International Journal of Modern Physics B ◽

10.1142/s0217979288000494 ◽

1988 ◽

Vol 02 (05) ◽

pp. 667-677 ◽

Cited By ~ 12

Author(s):

I. E. Dzyaloshinskii ◽

V. M. Yakovenko

Keyword(s):

Fermi Surface ◽

Hubbard Model ◽

Weak Coupling ◽

Weak Coupling Limit ◽

Two Dimensional ◽

Coupling Theory ◽

Strong Difference ◽

Effective Charges ◽

Weak Coupling Theory

In the model of two-dimensional electrons with a square Fermi surface , ln 2-parquet equations are derived and numerically solved. It is suggested that this model can describe La 2 CuO 4 in the weak coupling limit. The main result is a strong difference between the Hubbard model with one charge and the model with four effective charges, describing an interaction of a general form.

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An obstacle to sub-AdS holography for SYK-like models

Journal of High Energy Physics ◽

10.1007/jhep03(2021)094 ◽

2021 ◽

Vol 2021 (3) ◽

Author(s):

Pengfei Zhang ◽

Yingfei Gu ◽

Alexei Kitaev

Keyword(s):

Lyapunov Exponent ◽

Weak Coupling ◽

Kinetic Coefficient ◽

Weak Coupling Limit ◽

Branching Time ◽

Quasiparticle Lifetime

Abstract We argue that “stringy” effects in a putative gravity-dual picture for SYK-like models are related to the branching time, a kinetic coefficient defined in terms of the retarded kernel. A bound on the branching time is established assuming that the leading diagrams are ladders with thin rungs. Thus, such models are unlikely candidates for sub-AdS holography. In the weak coupling limit, we derive a relation between the branching time, the Lyapunov exponent, and the quasiparticle lifetime using two different approximations.

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Modes of Interannual Tropical Ocean–Atmosphere Interaction—a Unified View. Part II: Analytical Results in the Weak-Coupling Limit

Journal of the Atmospheric Sciences ◽

10.1175/1520-0469(1993)050<3504:moitoi>2.0.co;2 ◽

1993 ◽

Vol 50 (21) ◽

pp. 3504-3522 ◽

Cited By ~ 78

Author(s):

J. David Neelin ◽

Fei-Fei Jin

Keyword(s):

Weak Coupling ◽

Weak Coupling Limit ◽

Tropical Ocean ◽

Analytical Results ◽

Ocean Atmosphere ◽

Unified View ◽

Ocean Atmosphere Interaction ◽

Atmosphere Interaction

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EFFECTS OF c-AXIS HOPPING IN THE INTERLAYER TUNNELING MODEL OF HIGH-Tc LAYERED CUPRATES

International Journal of Modern Physics B ◽

10.1142/s0217979299001600 ◽

1999 ◽

Vol 13 (13) ◽

pp. 1619-1632

Author(s):

BIPLAB CHATTOPADHYAY ◽

A. N. DAS

Keyword(s):

Experimental Data ◽

Transition Temperature ◽

Cuprate Superconductors ◽

Interlayer Coupling ◽

Superconducting Gap ◽

Tunneling Model ◽

High Tc ◽

Optimal Doping ◽

Pair Tunneling ◽

Layered Cuprates

We consider the interlayer pair-tunneling model for layered cuprates, including an effective single particle hopping along the c-axis. A phenomenological suppression of the c-axis hopping matrix element, by the pseudogap in cuprate superconductors, is incorporated. At optimal doping, quantities characteristic to the superconducting state, such as the transition temperature and the superconducting gap are calculated. Results from our calculations are consistent with the experimental observations with the noteworthy point that, the superconducting gap as a function of temperature shows excellent match to the experimental data. Predictions within the model, regarding T c variation with interlayer coupling, are natural outcomes which could be tested further.

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