Doping dependence of the superconducting transition temperature in high-Tc systems

1996 ◽  
Vol 103 (2) ◽  
pp. 145-147 ◽  
Author(s):  
J. Schmalian ◽  
S. Grabowski ◽  
K.H. Bennemann
Keyword(s):  
Transition Temperature ◽  
Superconducting Transition Temperature ◽  
Superconducting Transition ◽  
High Tc ◽  
Doping Dependence

A Device for Measuring High-TC Superconductor Transition Temperature with Electric Transport and AC Susceptibility Methods Based on Small Cryocooler Cooling

2013 ◽  
Vol 745-746 ◽  
pp. 152-157 ◽  
Author(s):  
San Sheng Wang ◽  
Xiao Shuai Ning ◽  
Xiang Hua Chu ◽  
Hua Li
Keyword(s):  
Transition Temperature ◽  
Superconducting Transition Temperature ◽  
Ac Susceptibility ◽  
Transition Curve ◽  
Secondary Coil ◽  
Electric Transport ◽  
Superconducting Transition ◽  
High Tc ◽  
High Tc Superconductor ◽  
Lock In

A device for measuring high-TC superconducting transition temperature in a small cryocooler is described which allows a samples temperature to fall steadily from room temperature to 45K. This cryocooler not only meets the high-TC superconductors measurement requirements, but also yields accurate measurement results under ambient conditions. In this device, two measurement methods for measuring high-TC superconducting transition temperature are applied: the electric transport and the AC susceptibility. The former adopts a four-wire method to eliminate the contact resistance between the leads and the sample. During the measurement process the current reversal method for datum processing is applied to eliminate the thermoelectric voltages; this ensures the repeatability error less than 0.4K in the measurement of the superconducting transition temperature. The AC susceptibility method adopts a lock-in amplifier to provide an AC voltage signal for the primary coil, and then lock-in amplifier is used to measure the electrical signals of the secondary coil according to the AC magnetic susceptibility values. The advantage of this device is that by merely changing the position of the sample in the vacuum chamber, the R-T curve and the χ-T curve of a superconducting sample in the same temperature range can be automatically recorded, which provides reliable data for high-TC superconductor transition curve measurement.

THEORY OF THE ISOTOPE EFFECT AND SUPERCONDUCTING TRANSITION TEMPERATURE IN HIGH-Tc OXIDES

2011 ◽  
Vol 25 (26) ◽  
pp. 2069-2078 ◽  
Author(s):  
A. BECHLAGHEM ◽  
D. BOURBIE
Keyword(s):  
Experimental Data ◽  
Transition Temperature ◽  
Fermi Level ◽  
Isotope Effect ◽  
Qualitative Agreement ◽  
Superconducting Transition Temperature ◽  
Superconducting Transition ◽  
Van Hove Singularity ◽  
High Tc ◽  
Analytical Expressions

Analytical expressions for the superconducting transition temperature Tc and the isotope coefficient α have been obtained for the case where the Fermi level is close to the van Hove singularity. In this approach, we consider two interactions, the first related to the phonons and the second relevant to the magnetic excitations. Our result shows that the isotope coefficient α decreases with the superconducting transition temperature Tc in qualitative agreement with experimental data.

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.

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