Coexistence of the s wave (on site) pairing and d wave (off site) pairing of high TC superconductors

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.

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Theory of NMR and specific heat for extended s-wave and d-wave pairing states in high Tc superconductors

Physica B Condensed Matter ◽

10.1016/s0921-4526(09)80124-5 ◽

1990 ◽

Vol 165-166 ◽

pp. 1077-1078 ◽

Cited By ~ 1

Author(s):

C.T. Rieck ◽

D. Fay ◽

L. Tewordt

Keyword(s):

Specific Heat ◽

High Tc Superconductors ◽

S Wave ◽

High Tc ◽

Wave Pairing ◽

D Wave

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

Symmetry ◽

10.3390/sym3040699 ◽

2011 ◽

Vol 3 (4) ◽

pp. 699-749 ◽

Cited By ~ 12

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.

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

International Journal of Modern Physics B ◽

10.1142/s021797929800199x ◽

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.

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Qualitative Picture of a New Mechanism for High-Tc Superconductors

International Journal of Modern Physics B ◽

10.1142/s0217979203020879 ◽

2003 ◽

Vol 17 (18n20) ◽

pp. 3284-3292

Author(s):

Chia-Ren Hu

Keyword(s):

Short Range ◽

Coulomb Repulsion ◽

Tunneling Conductance ◽

High Tc Superconductors ◽

Nernst Effect ◽

High Tc ◽

Ferromagnetic Order ◽

Wave Nature ◽

Qualitative Picture ◽

D Wave

Xu et al. observed enhanced Nernst effect and Iguchi et al. observed patched diamagnetism, both well above Tc in underdoped high-Tc superconductors (HTSCs). A new mechanism is proposed here, which seems to naturally explain, at least qualitatively, these observations, as well as the d-wave nature and continuity of pseudogap and pairing gap, the tunneling conductance above Tc, as well as T*(x), Tν(x), Tc(x), etc. This mechanism combines features of dynamic charged stripes, preformed pairs, and spin-bags: At appropriete doping levels, the doped holes (and perhaps also electrons) will promote the formation of anti-phase islands in short-range anti-ferromagnetic order. On the boundary of each such island reside two doped carriers; the unscreened Coulomb repulsion between them stabilizes the island's size. Superconductivity results when such "pre-formed pairs" Bose-condense.

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MAGNETIC AND SUPERCONDUCTING PROPERTIES OF HIGH-Tc SUPERCONDUCTORS

International Journal of Modern Physics B ◽

10.1142/s0217979295000240 ◽

1995 ◽

Vol 09 (06) ◽

pp. 633-677 ◽

Cited By ~ 2

Author(s):

R. VIJAYARAGHAVAN ◽

L.C. GUPTA

Keyword(s):

Flux Line ◽

Parent Material ◽

High Tc Superconductors ◽

S Wave ◽

Important Ingredient ◽

Magnetic Systems ◽

High Tc ◽

Antiferromagnetic Ordering ◽

Magnetic Transport ◽

Very High

High-Tc superconductors, distorted-perovskite cuprates, are derived, by means of suitable doping, from a Mott-insulating and antiferromagnetic parent material. The most important ingredient of their structure is the stacks of Cu-O planes which carry superconductivity. Magnetic, transport and other properties that characterize the supercon-ducting state are very unusual and highly anisotropic. Density of states at the Fermi level in these materials is rather small but Tc is very high (highest reported Tc~125 K). In the high-Tc systems that contain magnetic moment bearing rate earth (RE)-atoms, antiferromagnetic ordering (TN<2 K) of RE-moments coexists with superconductivity. Some of them are ideal two-dimensional magnetic systems. Flux line lattices in these materials have rather unusual structural properties. There are both hole-type as well as electron-type superconductors. The available experimental evidence does not favour odd-parity pairing. It is not yet clear, however, whether even-parity pairing is d-wave or s-wave type. Antiferromagnetic fluctuations may be possible mechanism of Cooper pairing. Anyonic superconductivity is ruled out.

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ON THE ORIGIN OF d-WAVE PAIR FUNCTIONS IN HIGH-Tc SUPERCONDUCTIVITY

International Journal of Modern Physics B ◽

10.1142/s0217979206035606 ◽

2006 ◽

Vol 20 (23) ◽

pp. 3279-3305

Author(s):

DANIEL C. MATTIS

Keyword(s):

Band Model ◽

Checkerboard Pattern ◽

Coupling Constant ◽

S Wave ◽

High Tc ◽

Lumped Parameter ◽

Intimate Relation ◽

A Charge ◽

Fine Tune ◽

D Wave

We argue that the usual Hubbard's model produces only s-wave pairing functions and, even then, only at unphysically large values of the lumped parameter J≡4t2/U. It follows that a reliable theory of high-Tc superconductivity has to include additional features if it is to reproduce the d-wave gap. We test the effects of an alternating potential caused by a charge stripe, on the ground state of the Hubbard model in strong-coupling. If we "fine tune" we do find the d-waves. However, a better-formulated version of a three-band model yields a sturdier theory of pair formation in high-Tc superconductivity. The coupling constant g1=t2/V factors out, hence it serves only to establish the unit of energy; the underlying Hamiltonian is universal. We outline the principal properties of this model, including the intimate relation between charge-density stripes and the d-wave pair function, its rejection of 45° stripes (checkerboard pattern), and other concerns.

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