HIGH PRESSURE STUDY ON SOME HIGH-Tc SUPERCONDUCTORS

1995 ◽  
Vol 09 (20) ◽  
pp. 1259-1276 ◽  
Author(s):  
C. Y. HUANG ◽  
J. G. LIN ◽  
Z. J. HUANG
Keyword(s):  
High Pressure ◽  
Rare Earth ◽  
Transition Temperature ◽  
Pressure Effects ◽  
Superconducting Transition ◽  
High Tc Superconductors ◽  
Ionic Radii ◽  
High Tc ◽  
High Pressure Study ◽  
Good Agreement

We present a brief review on the pressure effects of some high temperature super-conductors. The examined systems include RBa 2 Cu 3 O 7, (R, Pr)Ba 2 Cu 3 O 7 and (ZnPc) y Bi 2 Sr 2 Ca 2 Cu 3 O 10, with R=rare earth elements and Pc=phthalocyanine. The results of the presssure effects on the superconducting transition temperature T c in these materials have, thus, not only revealed the origin of the T c -variation induced by the chemical substitution or intercalation, but have also confirmed the important roles played by the carrier concentration and T co (maximum T c ) on determining T c . Based on our experimental results, along with good agreement between our data and theory, we have clearly demonstrated that the variation of T c dominantly originates from the strains induced by the variation of the ionic radii or the intercalation of foreign molecules.

HIGH PRESSURE STUDIES OF SUPERCONDUCTING Ba1−xKxBiO3

1990 ◽  
Vol 04 (14) ◽  
pp. 935-944 ◽  
Author(s):  
Z.J. HUANG ◽  
C.Y. HUANG ◽  
P.H. HOR ◽  
R.L. MENG ◽  
Y.Q. WANG ◽  
...  
Keyword(s):  
High Pressure ◽  
Transition Temperature ◽  
Pressure Effects ◽  
Superconducting Transition ◽  
High Current ◽  
Applied Current ◽  
High Pressure Studies ◽  
Sample Resistance ◽  
State Resistance ◽  
Normal State Resistance

We have studied the pressure effects of superconducting Ba 1−x K x BiO 3 for x=0.25, 0.30, 0.35 and 0.40 up to ~16 kbar . The superconducting transition temperature, Tc, increases linearly with pressure, P. We have found that dTc/dP decreases with increasing Tc, and reaches ~0 around Tc~29 K. For the x=0.35 sample, resistance reappears below Tc for pressure >12 kbar. This resistance depends strongly on the applied current. It becomes greater than the normal state resistance and noisy at high current.

PRESSURE EFFECTS ON HIGH-Tc SUPERCONDUCTORS CURRENT TRANSFER

1991 ◽  
Vol 05 (20) ◽  
pp. 3255-3265 ◽  
Author(s):  
V.M. SVISTUNOV ◽  
A.I. D’YACHENKO ◽  
V. YU. TARENKOV
Keyword(s):  
Magnetic Field ◽  
High Pressure ◽  
Magnetic Fields ◽  
Pressure Effects ◽  
High Magnetic Fields ◽  
Magnetic Field Direction ◽  
Current Transfer ◽  
High Tc Superconductors ◽  
High Tc ◽  
The Magnetic Field

The efficiency of high pressure technique for the evidence of the Josephson nature of the intergranular contacts in metal ceramics has been demonstrated. With this technique it has been found that the abnormal hysteresis in fields of the order of tens kOe was not connected with the short-circuited contacts between the granules. The reason for the hysteresis lies in the ambiguity of the magnetization of the granules versus the change in the magnetic field direction. The critical current stability of the Josephson conteacts to high magnetic fields is due to both the inhomogeneity of the contacts and the existence of Abrikosov vortices within the superconducting electrode links.

HIGH PRESSURE STUDY OF La3Ni2B2Nx

1995 ◽  
Vol 09 (11n12) ◽  
pp. 731-736
Author(s):  
Y. CAO ◽  
R. L. MENG ◽  
C. W. CHU
Keyword(s):  
High Pressure ◽  
Transition Temperature ◽  
Superconducting Transition Temperature ◽  
Pressure Effect ◽  
Nominal Composition ◽  
Superconducting Transition ◽  
Superconducting Compounds ◽  
High Pressure Study

The pressure effect on the superconducting transition temperature (T c ) of the newly discovered compound with a nominal composition La 3 Ni 2 B 2 N x with a T c ~14 K has been determined up to 1.5 GPa. T c was found to decrease linearly at a rate of –0.9 K/GPa, which is much greater than that of similar superconducting compounds, LuNi 2 B 2 C and Lu 2 Ni 2 B 2 C 2, while the compound resistivity remains unchanged. Reasons for the observation remain unknown.

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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