scholarly journals Aspects of Optical Properties in Conventional and Oxide Superconductors

1997 ◽  
Vol 50 (6) ◽  
pp. 975 ◽  
Author(s):  
F. Marsiglio ◽  
J. P. Carbotte
Keyword(s):  
Inelastic Scattering ◽  
Oxide Superconductors ◽  
S Wave ◽  
Temperature Dependent ◽  
High Tc ◽  
The Real ◽  
Scattering Rate ◽  
Wave Symmetry ◽  
High Tc Cuprates ◽  
D Wave

We review the effect of elastic and inelastic scattering on the normal state infrared conductivity, and describe modifications to the real and imaginary parts which result from a transition to an s-wave superconducting state. The zero frequency limit of the imaginary part is related to the temperature-dependent penetration depth and, at finite frequency, provides information about the superconducting gap. In the high Tc cuprates the gap appears to have d-wave symmetry. This profoundly modifies both the real and the imaginary parts of the optical conductivity. After describing these modifications we introduce the conductivity-derived scattering rate, which directly probes the inelastic scattering processes, and is much larger in the oxides than in conventional superconductors. This quantity is also significantly modified by the d-wave symmetry of the gap.

Pair Symmetry and Degree of Gap Depression at S-I Interfaces in HTS Josephson Junctions

1999 ◽  
Vol 13 (09n10) ◽  
pp. 1301-1306
Author(s):  
G. A. Ummarino ◽  
R. S. Gonnelli ◽  
C. Bravi ◽  
Masumi Inoue
Keyword(s):  
Josephson Junctions ◽  
Order Parameter ◽  
Reference Value ◽  
High Tc Superconductors ◽  
S Wave ◽  
General Reference ◽  
High Tc ◽  
Wave Symmetry ◽  
Set Up ◽  
D Wave

A new possible indirect way of testing pair symmetry in high-Tc superconductors has been set up. The degree of intrinsic gap depression at Superconductor-Insulator [S-I] interfaces required to match Ic(T)Rn(T) data in HTS Josephson junctions depends on the pair symmetry of the material itself, so that an higher fraction of d-wave symmetry for the order parameter requires less gap depression, while an higher fraction of s-wave corresponds to a larger degree of gap depression. In order to obtain a general reference value for the intrinsic amount of gap depression at S-I interfaces the de Gennes condition has been used, and resulting reduced Ic(T)Rn(T) data have been calculated in the framework of a mixed (s+id)-wave pair symmetry for the depressed order parameter ranging from pure s to pure d-wave. This model has been tentatively applied to two junctions' made of very different HTSs: YBCO and BKBO, yielding a result of almost pure d-wave for YBCO and of pure s-wave for BKBO.

Effects of d-wave symmetry in high Tc step-edge Josephson junctions

2000 ◽  
Vol 341-348 ◽  
pp. 1473-1474 ◽  
Author(s):  
Soon-Gul Lee ◽  
Yunseok Hwang ◽  
Jin-Tae Kim ◽  
Gun Yong Sung
Keyword(s):  
Josephson Junctions ◽  
Step Edge ◽  
High Tc ◽  
Wave Symmetry ◽  
D Wave

DENSITY OF STATES AND ORDER PARAMETER IN DIRTY SUPERCONDUCTORS WITH A WEAKLY BROKEN d-WAVE SYMMETRY

1996 ◽  
Vol 10 (12) ◽  
pp. 537-544 ◽  
Author(s):  
SERGEI V. POKROVSKY
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Density Of States ◽  
Order Parameter ◽  
Zero Temperature ◽  
Scattering Rate ◽  
Wave Symmetry ◽  
Direct Calculations ◽  
D Wave ◽  
Gapless Superconductivity

It is shown by direct calculations that in a superconductor with a slightly violated d-wave symmetry of the order parameter (OP) the impurity driven phase transition from the gapless superconductivity to a state with a finite gap takes place at zero temperature. The corresponding scattering rate is close to the value at which the superconductivity vanishes in the d-superconductor. The behavior of the transition temperature, the OP and the density of states (DOS) is analyzed. The model is plausibly relevant to the BSCCO 2:2:1:2.

scholarly journals d-Wave Superconductivity and s-Wave Charge Density Waves: Coexistence between Order Parameters of Different Origin and Symmetry

Symmetry ◽  
2011 ◽  
Vol 3 (4) ◽  
pp. 699-749 ◽  
Author(s):  
Toshikazu Ekino ◽  
Alexander M. Gabovich ◽  
Mai Suan Li ◽  
Marek Pękała ◽  
Henryk Szymczak ◽  
...  
Keyword(s):  
Charge Density ◽  
Charge Density Waves ◽  
Order Parameters ◽  
Density Waves ◽  
S Wave ◽  
High Tc ◽  
Energy Gaps ◽  
Theoretical Predictions ◽  
Different Origin ◽  
D Wave

A review of the theory describing the coexistence between d-wave superconductivity and s-wave charge-density-waves (CDWs) is presented. The CDW gapping is identified with pseudogapping observed in high-Tc oxides. According to the cuprate specificity, the analysis is carried out for the two-dimensional geometry of the Fermi surface (FS). Phase diagrams on the σ0 − α plane—here, σ0 is the ratio between the energy gaps in the parent pure CDW and superconducting states, and the quantity 2α is connected with the degree of dielectric (CDW) FS gapping—were obtained for various possible configurations of the order parameters in the momentum space. Relevant tunnel and photoemission experimental data for high-Tc oxides are compared with theoretical predictions. A brief review of the results obtained earlier for the coexistence between s-wave superconductivity and CDWs is also given.

D-WAVE CHECKERBOARD BOSE CONDENSATE OF MOBILE BIPOLARONS

2007 ◽  
Vol 21 (13n14) ◽  
pp. 2301-2312 ◽  
Author(s):  
A. S. ALEXANDROV
Keyword(s):  
Particle Density ◽  
Center Of Mass ◽  
Bose Condensate ◽  
Real Space ◽  
Temperature Dependent ◽  
Finite Center ◽  
Electron Phonon Interaction ◽  
Single Particle Density ◽  
Wave Symmetry ◽  
D Wave

Strong finite-range electron-phonon interaction (EPI) bounds carriers into small mobile bipolarons. The Bogoliubov-de Gennes (BdG) equations are formulated and solved in the strong-coupling limit, when small bipolarons bose-condense with finite center-of-mass momentum, K ≠ 0. There are two energy scales in this regime, a temperature independent incoherent gap Δp and a temperature dependent coherent gap Δc(T, R) modulated in the real space, R. The order parameter has d-wave symmetry in R-space and the single-particle density of states (DOS) reveals checkerboard modulations similar to the checkerboard tunnelling DOS observed in cuprates.

scholarly journals ELECTRONIC BOUND STATES IN PARITY-PRESERVING QED3 APPLIED TO HIGH-Tc CUPRATE SUPERCONDUCTORS

2003 ◽  
Vol 18 (05) ◽  
pp. 725-741 ◽  
Author(s):  
H. R. CHRISTIANSEN ◽  
O. M. DEL CIMA ◽  
M. M. FERREIRA ◽  
J. A. HELAYËL-NETO
Keyword(s):  
Bound States ◽  
Cuprate Superconductors ◽  
Energy Scale ◽  
Spontaneous Breaking ◽  
Electron Interaction ◽  
Oxide Superconductors ◽  
S Wave ◽  
High Tc ◽  
Pair Condensation ◽  
Copper Oxide Superconductors

We consider a parity-preserving QED 3 model with spontaneous breaking of the gauge symmetry as a framework for the evaluation of the electron–electron interaction potential underlying high-T c superconductivity. The fact that the resulting potential, -CsK0(Mr), is non-confining and "weak" (in the sense of Kato) strongly suggests the mechanism of pair-condensation. This potential, compatible with an s-wave order parameter, is then applied to the Schrödinger equation for the sake of numerical calculations, thereby enforcing the existence of bound states. The results worked out by means of our theoretical framework are checked by considering a number of phenomenological data extracted from different copper oxide superconductors. The agreement may motivate a deeper analysis of our model viewing an application to quasiplanar cuprate superconductors. The data analyzed here suggest an energy scale of 1–10 meV for the breaking of the U(1)-symmetry.

On the Origin of Zero-Bias Conductance Peak in High-Tc Superconductors

1998 ◽  
Vol 12 (29n31) ◽  
pp. 3027-3030
Author(s):  
Alexander B. Nazarenko ◽  
Ernst A. Pashitskii ◽  
Alexander E. Pashitskii
Keyword(s):  
Elastic Scattering ◽  
Order Parameter ◽  
Magnetic Impurities ◽  
High Tc Superconductors ◽  
Zero Bias ◽  
High Tc ◽  
Conductance Peak ◽  
Wave Symmetry ◽  
Zero Bias Conductance ◽  
D Wave

We show that the zero-bias conductance peak observed in tunnel and point junctions of cuprates can be a consequence of "unitary" elastic scattering of the carriers by non-magnetic impurities in the vicinity of the junction interface and d-wave symmetry of the order parameter.

Ginzburg–Landau Equations for a d-Wave Superconductor with Paramagnetic Impurities

1998 ◽  
Vol 12 (10) ◽  
pp. 1069-1095 ◽  
Author(s):  
Wonkee Kim ◽  
C. S. Ting
Keyword(s):  
Transition Temperature ◽  
Born Approximation ◽  
Wave Interaction ◽  
London Penetration Depth ◽  
S Wave ◽  
Ginzburg Landau ◽  
Paramagnetic Impurities ◽  
Wave Symmetry ◽  
Ginzburg Landau Equations ◽  
D Wave

Ginzburg–Landau (GL) equations for a d-wave superconductor with a repulsive s-wave interaction between electrons in the presence of paramagnetic impurities are microscopically derived based on the Born approximation. The diagrammatic relationships for the impurity-averaged product of Green's functions are algebraically established. The effect of paramagnetic impurities on the transition temperature and the London penetration depth are discussed. GL equations for a superconductor with both s-wave and d-wave pairing interactions are also examined. We show that the transition temperature for a superconductor with an s-wave symmetry is suppressed twice as rapidly as that with a d-wave symmetry in the dilute impurity limit if the strength of the spin-non-flip scattering is much weaker than the spin-flip interaction.

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