Identifying the Pairing Mechanism in High-Tc Superconductors

1989 ◽  
Vol 156 ◽  
Author(s):  
J.B. Goodenough ◽  
A. Manthiram ◽  
J. Zhou
Keyword(s):  
Stress Relief ◽  
Redox Couple ◽  
Oxide Superconductors ◽  
High Tc Superconductors ◽  
Pairing Mechanism ◽  
Strong Electron ◽  
High Tc ◽  
Two Factors ◽  
High Transition ◽  
Copper Oxide Superconductors

ABSTRACTIt is argued that the origin of the high transition temperatures observed in Ba1−xKxBiO3 and the copper-oxide superconductors with perovskite-related structures is due to two factors: (1) overlap of a partially filled σ* band of primarily cation character and a π or π* band of mostly O-2pπ parentage permits charge transfer between cation and anion subarrays with oxygen-atom displacement perpendicular to a M-O-M bond axis and (2) bondlength mismatch places the M-O-M bondlength under a compressive or tensile stress. Relief of a compressive stress by the bending of a M-O-M bond from 180° introduces a strong electron-lattice interaction with holes; a 180° Cu-O-Cu bond allows strong electronlattice coupling with electrons of a Cu2+/+ redox couple, but not with holes in a Cu3+/2+redox couple.

Theories of High Tc Superconductors

1987 ◽  
Vol 99 ◽  
Author(s):  
John Bardeen
Keyword(s):  
Low Temperatures ◽  
Landau Theory ◽  
3D Models ◽  
Oxide Superconductors ◽  
High Tc Superconductors ◽  
Pairing Interaction ◽  
Ginzburg Landau ◽  
High Tc ◽  
Wide Range ◽  
High Transition

ABSTRACTMany theories have been given to account for the high transition temperatures in the oxide superconductors. While most are based on pairing, they differ as to the origin of the attractive interaction that gives rise to the pairs and whether the pairing is weak or strong. If weak(λ < ∼ 0.5), the energy range of the pairing interaction must be wider than is consistent with one mediated solely by phonons. With measurements on single crystals becoming available, giving data covering a wide range of frequencies and temperatures, it is possible to narrow down the possible options. The data show that anisotropie 3D models are required. Observed isotope shifts indicate that phonons must play a role, but additional mechanisms are likely necessary to account for the high T's. Thermal, magnetic and transport data are consistent with anisotropie Ginzburg-Landau theory near T, with expected departures at low temperatures.

POSSIBLE MECHANISM OF PAIRING IN HIGH Tc SUPERCONDUCTORS: A MULTI-COMPONENT PLASMA MODEL

1988 ◽  
Vol 02 (05) ◽  
pp. 873-881
Author(s):  
J. Mahanty ◽  
M. P. Das
Keyword(s):  
Interaction Potential ◽  
Oxide Superconductors ◽  
Plasma Model ◽  
High Tc Superconductors ◽  
High Tc ◽  
Gap Equation ◽  
Ion Plasma ◽  
Electrons And Ions ◽  
Component Plasma ◽  
High Transition

Screening of a pair of point charges in a medium of electrons and ions is studied using the hydrodynamical model, treating the system as a multi-component plasma. When some of the ion plasma branches possess negative dispersion, the interaction potential of the pair can become attractive and large in certain regions of momentum space under certain conditions. By using this potential in the BCS gap equation, high transition temperatures have been obtained. Applicability of this model to oxide superconductors is discussed.

scholarly journals Tuning from failed superconductor to failed insulator with magnetic field

2019 ◽  
Vol 5 (6) ◽  
pp. eaav7686 ◽  
Author(s):  
Yangmu Li ◽  
J. Terzic ◽  
P. G. Baity ◽  
Dragana Popović ◽  
G. D. Gu ◽  
...  
Keyword(s):  
Theoretical Perspective ◽  
Three Dimensional ◽  
Oxide Superconductors ◽  
Pairing Mechanism ◽  
Spin Correlations ◽  
Electron Pairing ◽  
Copper Oxide Superconductors ◽  
Charge Modulations ◽  
Antiferromagnetic Spin ◽  
Local Segregation

Do charge modulations compete with electron pairing in high-temperature copper oxide superconductors? We investigated this question by suppressing superconductivity in a stripe-ordered cuprate compound at low temperature with high magnetic fields. With increasing field, loss of three-dimensional superconducting order is followed by reentrant two-dimensional superconductivity and then an ultraquantum metal phase. Circumstantial evidence suggests that the latter state is bosonic and associated with the charge stripes. These results provide experimental support to the theoretical perspective that local segregation of doped holes and antiferromagnetic spin correlations underlies the electron-pairing mechanism in cuprates.

THE ENERGY GAP IN THE HIGH-Tc COPPER OXIDE SUPERCONDUCTORS

1993 ◽  
Vol 07 (03) ◽  
pp. 143-153 ◽  
Author(s):  
YONGHONG LI ◽  
CHARLES M. LIEBER
Keyword(s):  
Transition Temperature ◽  
Energy Loss ◽  
High Temperature Superconductor ◽  
Energy Gap ◽  
Low Energy ◽  
Oxide Superconductors ◽  
High Tc ◽  
Resolution Electron ◽  
Copper Oxide Superconductors ◽  
Electron Energy Loss

We briefly review high-resolution electron energy loss spectroscopy (HREELS) studies of the low energy excitations in the high-temperature superconductor Bi 2 Sr 2 CaCu 2 O 8. HREELS has been used to determine the magnitude and temperature dependence of the energy gap (2Δ) for Bi 2 Sr 2 CaCu 2 O 8 single crystals. Below the transition temperature low-energy excitations are detected in the energy loss spectra. Because the energy loss spectra are proportional to the real part of the frequency dependent resistivity, ρR(ω), the energy gap can be determined directly from the HREEL data. At low temperature 2Δ = 6kT c and Δ develops sharply for T < T c . The constraints that these new results place on potential mechanisms of superconductivity are discussed.

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.

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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