Correlation between the superconducting transition temperature and the spacing of Cu-O2 sheets in the copper-oxide superconductors

1990 ◽  
Vol 167 (5-6) ◽  
pp. 515-519 ◽  
Author(s):  
H. Nobumasa ◽  
K. Shimizu ◽  
T. Kawai
Keyword(s):  
Transition Temperature ◽  
Copper Oxide ◽  
Superconducting Transition Temperature ◽  
Oxide Superconductors ◽  
Superconducting Transition ◽  
Copper Oxide Superconductors

Superconductivity at High Temperatures Without Copper: Ba1-xKxBiO3

MRS Bulletin ◽  
1989 ◽  
Vol 14 (1) ◽  
pp. 49-52 ◽  
Author(s):  
R.J. Cava ◽  
B. Batlogg
Keyword(s):  
Transition Temperature ◽  
Copper Oxide ◽  
Superconducting Transition Temperature ◽  
Parent Compound ◽  
Magnetic Interactions ◽  
Chemical System ◽  
Oxide Superconductors ◽  
Theoretical Point ◽  
Superconducting Transition ◽  
Magnetic Fluctuations

Before the pioneering work of Bednorz and Müller in finding superconductivity near 30 K in lanthanum-barium-copper oxide,. oxide superconductors were well known, but perhaps not fully appreciated. Most anomalous among those superconductors was the perovskite structure material BaPb0.75Bi0.25O3, with a superconducting transition temperature (Tc) of 12 K2 and a surprisingly low density of states at the Fermi level. The increases in Tc for copper-oxide-based materials continue to generate worldwide excitement, but from both a chemical and theoretical point of view, high Tc superconductivity observed in a noncopper containing material is also of considerable interest.Recently we found that the simple cubic perovskite compound Ba0.6K0.4BiO3 displays a superconducting transition temperature near 30K—a Tc considerably higher than that of conventional superconductors and surpassed only by copper containing compounds. This material is in stark contrast to the now well-known copper oxides for two reasons: (1) superconductivity occurs within the framework of a three dimensionally connected bismuth-oxygen array (and not a 2-d array as in the Cu-O based compounds) and: (2) there are no magnetic fluctuations present in the chemical system, either in the superconductor itself or in the nonsuperconducting end member compound, eliminating the possibility that the high Tc might be caused by magnetic interactions. The parent compound BaBiO3 is, however, of considerable interest due to the presence of a structurally frozen charge disproportionation of the bismuth atoms, considered by many to be the electronic equivalent of the antiferromagnetism observed in the nonsuperconducting cuprate host compounds.The ideal undistorted perovskite ABO3 structure consists of a regular array of equally dimensioned BO6 octahedra sharing all corner oxygens with neighboring equivalent octahedra, with 180° B-O-B angles.

scholarly journals Paramagnetic Resonance as a Probe of the Spin Gap in Normal State of Superconductor

2011 ◽  
Vol 2011 ◽  
pp. 1-3
Author(s):  
Frank J. Owens
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Transition Temperature ◽  
Normal State ◽  
Oxide Superconductors ◽  
Superconducting Transition ◽  
Paramagnetic Resonance ◽  
Spin Gap ◽  
Order Of Magnitude ◽  
Copper Oxide Superconductors ◽  
Electron Paramagnetic

It is shown that electron paramagnetic resonance (EPR) can be used to observe the spin gap in copper oxide superconductors. The electron paramagnetic resonance spectra of the Cu2+ ion in underdoped show a pronounced decrease in intensity in the normal state as the temperature is lowered to 133 K, the superconducting transition temperature of the material. The decrease is attributed to a pairing of the Cu2+   spins to form a spin gap. A spin gap of 0.0533 eV is estimated from the data which is in order of magnitude agreement with values obtained from NMR measurements.

SUPERCONDUCTIVITY IN THE NEARLY HALF–FILLED HUBBARD MODEL WITH STRONG ON SITE CORRELATION

1988 ◽  
Vol 02 (05) ◽  
pp. 567-575 ◽  
Author(s):  
A. N. Das ◽  
P. Choudhury ◽  
B. Ghosh
Keyword(s):  
High Temperature ◽  
Transition Temperature ◽  
Hubbard Model ◽  
Density Of States ◽  
Fermi Energy ◽  
Strong Correlation ◽  
Superconducting Transition Temperature ◽  
Hole Concentration ◽  
Oxide Superconductors ◽  
Superconducting Transition

Superconductivity in a nearly half-filled Hubbard model with large on-site repulsion has been studied following the Hubbard's approximation. At T = 0, the Fermi energy touches the top of the lower Hubbard subband for n = 1, one electron per site in the system. For a particular density of states, sharply peaked at the centre of the band, the superconducting transition temperature is zero for n = 1 (zero hole concentration) and becomes maximum at a hole concentration of 1/3. The high temperature thermoelectric power of the oxide superconductors has been discussed, which indicates the strong correlation in the system.

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