Pairon Green’s function for high-Tc superconductors

2020 ◽  
pp. 2150080
Author(s):  
Radhika Chauhan ◽  
B. D. Indu
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Quantum Dynamics ◽  
Nodal Point ◽  
Superconducting Gap ◽  
Energy Relation ◽  
Gap Equation ◽  
Gap Ratio ◽  
Many Body Quantum Dynamics ◽  
The Many

Considering the many-body quantum dynamics, the pairon Green’s function has been developed via a Hamiltonian that encompasses the contribution of pairons, pairon-phonon interactions, anharmonicities, and defects. To obtain the renormalized pairon energy dispersion, the most relevant Born–Mayer–Huggins potential has been taken into account. The Fermi surface for the representative [Formula: see text] high-[Formula: see text] superconductor has been obtained via renormalized pairon energy relation. This revealed the [Formula: see text]-shape superconducting gap with a nodal point along [Formula: see text] direction. Further, the superconducting gap equation has been derived using the pairon density of states. The developed gap equation is the function of temperature, Fermi energy, and renormalized pairon energy. The temperature variation of the gap equation is found to be in good agreement with the BCS gap equation. Also, this reveals the reduced gap ratio ([Formula: see text] for [Formula: see text]) in the limit (5–8) of the reduced gap ratio designated for high-[Formula: see text] superconductors.

Superconducting gap anisotropy and d-wave pairing in YBa2Cu3O7−δ

2018 ◽  
Vol 32 (04) ◽  
pp. 1850035 ◽  
Author(s):  
Sanjeev K. Verma ◽  
Anushri Gupta ◽  
Anita Kumari ◽  
B. D. Indu
Keyword(s):  
High Temperature ◽  
Quantum Dynamics ◽  
High Temperature Superconductors ◽  
Nodal Point ◽  
Frequency Dispersion ◽  
Pairing Symmetry ◽  
Superconducting Gap ◽  
Phonon Field ◽  
Many Body Quantum Dynamics ◽  
The Many

Considering Born–Mayer–Huggins potential as a most suitable potential to study the dynamical properties of high-temperature superconductors (HTS), the many-body quantum dynamics to obtain phonon Green’s functions has been developed via a Hamiltonian that incorporates the contributions of harmonic electron and phonon fields, phonon field anharmonicities, defects and electron–phonon interactions without considering BCS structure. This enables one to develop the quasiparticle renormalized frequency dispersion in the representative high-temperature cuprate superconductor YBa2Cu3O[Formula: see text]. The superconducting gap shows substantial changes with increased doping. The in-plane gap study revealed a [Formula: see text]-shape gap with a nodal point along [Formula: see text] direction for optimum doping ([Formula: see text] = 0.16) and the nodal point vanished in underdoped and overdoped regimes. The d[Formula: see text] pairing symmetry is observed at optimum doping with the presence of s or d[Formula: see text] components ([Formula: see text] 3%) in underdoped and overdoped regimes.

Eine Approximation der Löwdinschen natürlichen Orbitale für Moleküle mit einer Green-Funktion-Methode

1972 ◽  
Vol 27 (4) ◽  
pp. 545-552 ◽  
Author(s):  
R. Albat
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Mass Operator ◽  
Ground States ◽  
Present Form ◽  
Many Body ◽  
Natural Orbitals ◽  
First Order ◽  
The Many ◽  
Closed Shells

Abstract An Approximation of Löwdin's Natural Orbitals for Molecules with a Green's Function Method The many-body-pertubation theorie of the single-particle Green's function is used to get an approximate first-order density matrix. Slightly modified SCF-orbitals form the basis for the expansion. The mass-operator in Dyson's equation is considered up to second order in the Perturbation. In the present form the method is only applicable to ground states with closed shells. The ground states of the molecules LiH and NH3 serve as examples to demonstrate the usefulness of the directly calculated natural orbitals for application in the C I-method. The natural orbitals give a much better convergence of the C I-expansion than the SCF-orbitals do.

scholarly journals Creating Nodes at Selected Locations in a Harmonically Excited Structure Using Feedback Control and Green’s Function

2019 ◽  
Vol 2019 ◽  
pp. 1-20 ◽  
Author(s):  
Bassam A. Albassam
Keyword(s):  
Steady State ◽  
Feedback Control ◽  
Green’S Function ◽  
Green's Function ◽  
Nodal Point ◽  
Control Force ◽  
Velocity Measurements ◽  
Numerical Examples ◽  
Control Forces

The paper deals with designing a control force to create nodal point(s) having zero displacements and/or zero slopes at selected locations in a harmonically excited vibrating structure. It is shown that the steady-state vibrations at desired points can be eliminated using feedback control forces. These control forces are constructed from displacement and/or velocity measurements using sensors located either at the control force position or at some other locations. Dynamic Green’s function is exploited to derive a simple and exact closed from expression for the control force. Under a certain condition, this control force can be generated using passive elements such as springs and dampers. Numerical examples demonstrate the applicability of the method in various cases.

Witnessing the boundary between Markovian and non-Markovian quantum dynamics: a Green’s function approach

2015 ◽  
Vol 14 (7) ◽  
pp. 2657-2672 ◽  
Author(s):  
Shibei Xue ◽  
Rebing Wu ◽  
Tzyh-Jong Tarn ◽  
Ian R. Petersen
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Quantum Dynamics ◽  
Function Approach
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