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.

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.

COOPER PAIRS AND TF-SCALED HIGH-TEMPERATURE SUPERCONDUCTIVITY

1991 ◽  
Vol 05 (12) ◽  
pp. 805-819 ◽  
Author(s):  
D. A. AGRELLO ◽  
V. C. AGUILERA-NAVARRO ◽  
M. DE LLANO ◽  
A. PLASTINO ◽  
CHRISTINA KELLER ◽  
...  
Keyword(s):  
High Temperature ◽  
Weak Coupling ◽  
Energy Gap ◽  
High Temperature Superconductivity ◽  
Muon Spin ◽  
High Temperature Superconductors ◽  
Strongly Coupled ◽  
Hartree Fock ◽  
Fermi Temperature ◽  
Gap Parameter

Abnormally-occupied single-fermion states, previously found to give lower total Hartree-Fock energies in numerous strongly-coupled neutral fluids, is shown to be a sufficient condition to give tighter-bound Cooper electron pairs for arbitrarily-weak coupling. Consequently, within the BCS picture where for weak-coupling the Cooper pair binding energy is simply related to the zero-temperature energy-gap parameter, which in turn is proportional to the critical temperature, T c , higher T c values which scale as the Fermi temperature are possible. This is consistent with recent muon-spin relaxation experiments on sixteen cuprate high-temperature superconductors.

ELECTRON-PHONON INTERACTION FOR AN ANALYTIC SOLUTION TO THE BCS EQUATION FOR THE HIGH TEMPERATURE SUPERCONDUCTORS

1991 ◽  
Vol 05 (20) ◽  
pp. 1349-1353 ◽  
Author(s):  
H. C. GUPTA
Keyword(s):  
High Temperature ◽  
Transition Temperature ◽  
Superconducting Transition Temperature ◽  
Analytic Solution ◽  
Energy Gap ◽  
High Temperature Superconductors ◽  
Superconducting Transition ◽  
Phonon Interaction ◽  
Electron Phonon Interaction ◽  
Gap Parameter

An energy dependent electron-phonon interaction has been used in the BCS equation. This provides an exactly solvable analytic solution to the BCS equation for the superconducting transition temperature and the gap parameter at absolute zero. These analytically obtained equations reduce to standard BCS form when temperature is small. These equations are applicable to low as well as high temperature superconductors successfully for their superconducting transition temperature and the energy gap parameter.

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.

ARPES studies of the superconducting gap in high-temperature superconductors

1996 ◽  
Author(s):  
H. Ding ◽  
M. R. Norman ◽  
John Giapintzakis ◽  
Juan C. Campuzano ◽  
H. Claus ◽  
...  
Keyword(s):  
High Temperature ◽  
High Temperature Superconductors ◽  
Superconducting Gap

Infrared and microwave spectra of an energy gap in high-temperature superconductors

1995 ◽  
Vol 51 (6) ◽  
pp. 3772-3782 ◽  
Author(s):  
C. T. Rieck ◽  
W. A. Little ◽  
J. Ruvalds ◽  
A. Virosztek
Keyword(s):  
High Temperature ◽  
Energy Gap ◽  
High Temperature Superconductors ◽  
Microwave Spectra
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