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.

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.

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.

THE EFFECT OF STRONG ELECTRON-PHONON INTERACTIONS ON THE INFRARED REFLECTANCE IN HIGH-Tc SUPERCONDUCTORS

1991 ◽  
Vol 05 (20) ◽  
pp. 1361-1365 ◽  
Author(s):  
S. Y. TIAN ◽  
M. H. LI ◽  
Z. X. ZHAO
Keyword(s):  
High Temperature Superconductors ◽  
Peak Position ◽  
Superconducting Gap ◽  
High Tc Superconductors ◽  
Phonon Interaction ◽  
Phonon Softening ◽  
Strong Electron ◽  
High Tc ◽  
Electron Phonon Interaction ◽  
And Shifts

We show that the model of charge-transfer fluctuation with LO phonons can unify the interpretation of the infrared features and the phonon softening at about 55 meV measured by neutron scattering experiments in high temperature superconductors. Based upon this model we demonstrate that reflectivity ratio of superconducting state to normal state is strongly modified as a result of strong electron-phonon interaction which is different from Holstein mechanism. A broad peak in the ratio reflectivity develops around the peak position of different neutron phonon density of states. This peak becomes stronger and shifts to a higher frequency as the coupling increases at lower temperatures. This situation complicates the interpretation of the ratio reflectivity peak as the superconducting gap.

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