NQR and NMR in High Tc Superconductors

1992 ◽  
Vol 47 (1-2) ◽  
pp. 7-11 ◽  
Author(s):  
K. Asayama ◽  
Y. Kitaoka ◽  
G.-q. Zheng
Keyword(s):  
High Temperature ◽  
Transition Temperature ◽  
Low Temperature ◽  
Spin Fluctuations ◽  
Superconducting Transition ◽  
High Tc Superconductors ◽  
High Tc ◽  
Pairing Correlations ◽  
Antiferromagnetic Spin ◽  
D Wave

AbstractRecent NQR and NMR experiments on La2-xSrxCuO4 , YBa2Cu3O7 , Tl2Ba2CuO6+y , and other compounds are reviewed. The antiferromagnetic spin fluctuations decrease in the order of La, Y, T1 compounds. In the normal state the T-dependence of (T1T)-1 is considered to follow the Curie- Weiss law at high temperature and the (Ti 7") = const law at low temperature. The T dependence of 1/T1 below Tc suggests strongly d-wave pairing. Correlations of the NQR frequency of 63Cu and 17O with the antiferromagnetic spin fluctuations and the superconducting transition temperature are discussed.

THE MULTILAYERED HIGH Tc SUPERCONDUCTORS; THE JOSEPHSON MODEL OF WEAK LINKS

1995 ◽  
Vol 09 (21) ◽  
pp. 2811-2820
Author(s):  
VALERY A. CHERENKOV
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
High Temperature Superconductors ◽  
Weak Links ◽  
High Tc Superconductors ◽  
Main Attention ◽  
Multilayered Structures ◽  
High Tc ◽  
Stimulation Of

The multilayered (N-S(D)-N)-types structures have been observed: there are the traditional Niobium low-temperature superconductors and new high-temperature superconductors. The main attention had been directed to the anisotropy, defectively and the stimulation of the superconductivity in the multilayered structures.

Structural and Superconducting Properties of RE1 - 2xPrxCaxSr0.8Ba1.2Cu3O7 - δ (RE = Er and Gd) High Tc Superconductors

2003 ◽  
Vol 17 (13) ◽  
pp. 2609-2622 ◽  
Author(s):  
N. Charoenthai ◽  
P. Winotai ◽  
R. Suryanarayanan ◽  
I. M. Tang
Keyword(s):  
Heat Treatment ◽  
High Temperature ◽  
Transition Temperature ◽  
Size Effect ◽  
High Temperature Superconductors ◽  
Superconducting Properties ◽  
High Tc Superconductors ◽  
High Tc ◽  
Oxygen Annealing ◽  
Ion Size

We report here on the structural and superconducting properties of RE 1 - 2x Pr x Ca x Sr 0.8 Ba 1.2 Cu 3 O 7 - δ (RE = Er and Gd, 0 ≤ x ≤ 0.2) high temperature superconductors. The transition temperature (Tc) of these compounds decreases when the Pr and Ca concentrations are increased. At constant Pr and Ca concentrations, the Tc of Er 1 - 2x Pr x Ca x Sr 0.8 Ba 1.2 Cu 3 O 7 - δ superconductor system is higher than that observed for the Gd 1 - 2x Pr x Ca x Sr 0.8 Ba 1.2 Cu 3 O 7 - δ system. For the Gd 0.8 Pr 0.1 Ca 0.1 Sr 0.8 Ba 1.2 Cu 3 O 7 - δ sample, after heating in argon followed by oxygen annealing, the orthorhombicity increases accompanied by 10 K increase in Tc. These results show that though our data indicate an ion-size effect, the Tc suppression rate dTc/dx depends very much on the heat treatment adopted to prepare the samples.

ANHARMONIC MODEL FOR HIGH-Tc SUPERCONDUCTORS

1987 ◽  
Vol 01 (03n04) ◽  
pp. 1071-1088 ◽  
Author(s):  
N.M. Plakida ◽  
V.L. Aksenov ◽  
S.L. Drechsler
Keyword(s):  
Experimental Data ◽  
Transition Temperature ◽  
Superconducting Transition Temperature ◽  
Superconducting Transition ◽  
High Tc Superconductors ◽  
High Tc ◽  
Perovskite Type

A considerable enhencement of the superconducting transition temperature Tc in perovskite-type oxides is explained in the framework of the anharmonic model for superconductors with structurally unstable lattices. It is shown that interaction of electrons with highly anharmonic oxigen-ion vibrations of a rotational type results in a sufficiently large couplings constant λ. The obtained estimation for Tc is in agreement with experimental data for La(Y)BaCuO systems.

SUBGAP INDUCED BY BILAYER EFFECTS OF CuO2 PLANES IN HIGH Tc SUPERCONDUCTORS

2003 ◽  
Vol 17 (29n30) ◽  
pp. 1495-1500
Author(s):  
JE HUAN KOO ◽  
GUANGSUP CHO
Keyword(s):  
Transition Temperature ◽  
Superconducting Transition Temperature ◽  
Superconducting Transition ◽  
High Tc Superconductors ◽  
Zero Bias ◽  
High Tc ◽  
Zero Bias Conductance

The bilayer effects of CuO 2 planes in high-T c superconductors are investigated. The interaction between a CuO 2 bilayer is found to induce a subgap far below the superconducting transition temperature T c . It is also shown that zero-bias-conductance-peaks (ZBCP) above T c are due to a Kondo-type effect as for low-T c superconductors, but ZBCP far below T c originating from this bilayer effects are different from traditional explanations.

COMMON MAGNETIC ORIGIN OF THE RESONANCE PEAK AND INCOMMENSURATION IN HIGH-Tc SUPERCONDUCTORS

2000 ◽  
Vol 14 (29n31) ◽  
pp. 3334-3341 ◽  
Author(s):  
C. D. BATISTA ◽  
G. ORTIZ ◽  
A. V. BALATSKY
Keyword(s):  
Transition Temperature ◽  
Superconducting Transition Temperature ◽  
Cuprate Superconductors ◽  
Resonance Peak ◽  
Low Energy ◽  
Unified Theory ◽  
Superconducting Transition ◽  
High Tc Superconductors ◽  
High Tc ◽  
Magnetic Origin

We present a unified theory for the resonance peak and low-energy incommensurate response observed in high-Tc cuprate superconductors. The origin of both features is purely magnetic and they represent universal features signaling the existence of an incommensurate spin state both below and above the superconducting transition temperature. We argue that the resonance peak is the reflection of commensurate antiferromagnetism. Our theoretical scenario gives an account of the main universal features observed in various families of superconductors and predicts those that have not been observed yet experimentally.

TUNNELLING SPECTROSCOPY OF HIGH-TC SUPERCONDUCTORS

1993 ◽  
Vol 07 (01n03) ◽  
pp. 123-126 ◽  
Author(s):  
TH. BECHERER ◽  
J. KOWALEWSKI ◽  
TH. WOLF ◽  
M. HUTH ◽  
W. ASSMUS ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Single Crystals ◽  
Theoretical Models ◽  
Differential Conductance ◽  
Superconducting Gap ◽  
Break Junction ◽  
Superconducting Transition ◽  
High Tc Superconductors ◽  
High Tc ◽  
Sharp Minima

Break junction tunnelling measurements were performed on YBa 2 Cu 3 O 7– and Bi 2 Sr 2 CaCu 2 O 8–single crystals and on polycrystalline ( Bi , Pb )2 Sr 2 Ca 2 Cu 3 O 10–samples. In the case of Bi 2 Sr 2 CaCu 2 O 8 the superconducting gap as evaluated from the peak-to-peak distance is Δab = (21.2 ± 2.8) meV , i.e. 2∆ab/kBTc = (5.5 ± 0.8). The differential conductance curves are similar to those of conventional strong coupling superconductors but with a much larger smearing, that cannot be explained with any of the theoretical models proposed so far. The measurements on YBa 2 Cu 3 O 7 show a strong linear background in the conductance. After subtraction of the background, peaks are discernible at ±21 meV, which yields 2∆ab/kBTc ≈ 2.8 if SIS tunnelling is assumed. The conductance curves of the ( Bi , Pb )2 Sr 2 Ca 2 Cu 3 O 10–polycrystals are dominated by the appearance of sharp minima below the superconducting transition temperature. The temperature dependence of these minima can be fitted well by the BCS behaviour.

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