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.

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.

scholarly journals The Gap and the Upper Critical FieldHc2as Function of Doping for High-TcCuprates

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
S. Orozco ◽  
R. M. Méndez-Moreno ◽  
M. A. Ortiz
Keyword(s):  
High Temperature ◽  
Critical Field ◽  
Energy Gap ◽  
High Temperature Superconductors ◽  
Upper Critical Field ◽  
Superconducting Gap ◽  
Phonon Interaction ◽  
As Doping ◽  
Electron Phonon Interaction ◽  
Wave Symmetry

The relation between thed-wave superconducting gapΔ0and the specific heat obtained with the Volovik effect is used to determine the upper critical fieldHc2as doping function, for high-temperature superconductors. A two-components model withd-wave symmetry, within the BCS framework, is introduced to describe the superconducting state. Generalized Fermi surface topologies are used in order to increase the density of states at the Fermi level, allowing the high-Tcvalues observed. The electron-phonon interaction is considered the most relevant mechanism for the high-Tccuprates, where the available phonon energy is provided by the half-breathing modes. The energy gap valuesΔ0calculated with this model are introduced to describe the variation of the upper critical fieldHc2as function of doping, forLa2-xSrxCuO4.

UniversalTcsuppression by in-plane defects in high-temperature superconductors: Implications for pairing symmetry

1996 ◽  
Vol 53 (18) ◽  
pp. 12454-12461 ◽  
Author(s):  
Sergey K. Tolpygo ◽  
J.-Y. Lin ◽  
Michael Gurvitch ◽  
S. Y. Hou ◽  
Julia M. Phillips
Keyword(s):  
High Temperature ◽  
High Temperature Superconductors ◽  
Pairing Symmetry

scholarly journals TUNNELING SPECTRA AND SUPERCONDUCTING GAP IN Bi2Sr2CaCu2O8+δ AND Tl2Ba2CuO6+δ

1999 ◽  
Vol 13 (29n31) ◽  
pp. 3721-3724 ◽  
Author(s):  
L. OZYUZER ◽  
J. F. ZASADZINSKI ◽  
N. MIYAKAWA
Keyword(s):  
High Temperature ◽  
Energy Gap ◽  
High Temperature Superconductors ◽  
Superconducting Gap ◽  
Coupling Ratio ◽  
Break Junctions ◽  
Underdoped Region ◽  
High Bias ◽  
Gap Parameter ◽  
Doping Range

Tunneling spectra are reported for Bi 2 Sr 2 CaCu 2 O 8+δ (Bi-2212) over a wide doping range using superconductor-insulator-superconductor (SIS) break junctions. The energy gap inferred from the tunneling data displays a remarkable monotonic dependence on doping, increasing to very large values in the underdoped region even as T c decreases. This leads to unphysically large values of the strong coupling ratio (~20). The tunneling spectra are qualitatively similar over the entire doping range even though the gap parameter, Δ, changes from 12 meV to 60 meV. Each spectrum exhibits dip and hump features at high bias with characteristic energies that scale with the superconducting gap. Tunneling spectra of near optimally-doped Tl 2 Ba 2 CuO 6+δ (Tl-2201) also display a weak dip feature in superconductor-insulator-normal metal (SIN) junctions. Generated SIS spectra of Tl-2201 are compared with measured spectra on Bi-2212 and it is concluded that the dip and hump features are generic to high temperature superconductors.

Perspectives on the Theory of the New High Tc Superconducting Oxides

MRS Bulletin ◽  
1989 ◽  
Vol 14 (1) ◽  
pp. 67-71 ◽  
Author(s):  
V.J. Emery
Keyword(s):  
High Temperature ◽  
High Temperature Superconductivity ◽  
High Temperature Superconductors ◽  
Many Body ◽  
Many Body Theory ◽  
The World ◽  
Superconducting Oxides ◽  
Will Force ◽  
The Many ◽  
Body Theory

There is a widespread feeling that the discovery of high temperature superconductors will force us to change our way of thinking about superconductivity in solids. It has steadily emerged that the simple free-electron picture is inadequate, that a new mechanism of superconductivity is most likely at work, and that modifications (if not outright revisions of the many-body theory) are needed. The situation is not entirely without precedent: much the same could have been said of superfluidity in liquid He. That, however, did not cause such a stir: it had been anticipated some 12 years before its eventual discovery, and the transition temperature of liquid He is so low that experiments have been confined to the few laboratories around the world with a milli-kelvin capability. Finally, the normal state of He was already wellunderstood, so that theorists were poised and ready to tackle the problems posed by the superfluid.Contrast the oxides. Even the rather extensive earlier studies of Ba1-x PbxBiO3 and other superconducting oxides did not prepare us for the advances of the past two years. Laboratories all over the world have been able to prepare and study the new superconductors rather easily, although well-characterized samples and incisive experiments have not been so easy to come by. The flood of new information poses a particular challenge for condensed matter theory — to distil the essence of these complicated multicomponent materials and to explain how the genie of high temperature superconductivity has escaped after so many years. Despite the existing understanding of the properties of oxides, much work remains to be done before we have a good grip on the many-body theory of these strongly correlated systems.

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