摘要:

EPR measurements of La1.82Sr0.18(Cu1−xZnx)O4compounds reveal that Zn doping induces formation of localized magnetic moments which, as has been found here, sit on Cu ions. At Zn concentration of 1 atomic percent, the quantity of these magnetic moments is close to the amount of substituted ions. This result is important for verifying diverse microscopic mechanisms of high‐Tcsuperconductivity.

ISSN:0094-243X    

DOI:10.1063/1.39733

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The anomalous normal state properties of the superconducting Cu‐O compounds have been calculated based on high hypothesis that there is no scales for low energy excitation of other than the temperature itself. (AIP)

ISSN:0094-243X    

DOI:10.1063/1.39717

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The electronic structure of copper metallo‐oxides of the type La2−xSrxCuO4and Nd2−xCexCuO4at high doping levels is discussed. Specifically, different possible explanations of the behavior of kinetic properties (notably the Hall effect) are suggested. It is concluded that the study of highly doped samples may provide useful information on the existence of electronic correlations in these systems and on their role in superconductivity.

ISSN:0094-243X    

DOI:10.1063/1.39726

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The origin of the quantum Hall effect is discussed in terms of the transmission probabilities of states at the Fermi‐level. A new argument for the existence of extended states near the center of the Landau level is given. Disequilibrium between edge and bulk currents in the extended state region is shown to give rise to non‐local and geometry‐dependent behavior of the Hall and longitudinal resistance. A model is discussed in which a new intensive ‘‘resistivity’’ is defined and used to generate quantitative predictions for the resistance of GaAs Hall conductors.

ISSN:0094-243X    

DOI:10.1063/1.39736

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The behavior of the optical transmission and reflection coefficients near the mobility edge of a disordered medium which elastically scatters light are discussed using a scaling theory. The transmission coefficient shows an interesting dependence on slab thickness. The coherent back scattering peak has a width determined by the correlation length and a height which also depends on this length. Both become small near the mobility edge. The effects of absorption are found to be important.

ISSN:0094-243X    

DOI:10.1063/1.39742

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The observed temperature singularities of electron light scattering (ELS) spectra for Tl2Ba2CaCu2O8, measured in different crystallographic directions and for different light polarizations, are interpreted as manifestations of strong anisotropy of the superconducting gap (2&Dgr;min<50 cm−1, 2&Dgr;max≊300 cm−1).

ISSN:0094-243X    

DOI:10.1063/1.39743

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A renormalization group analysis of interacting Fermion systems shows that there are two fundamentally different fixed points, Landau Fermi liquid theory and what has been called ‘‘Luttinger Liquid Theory’’ by Haldane, a type of state in which fluctuations of different quantum numbers—e.g., charge and spin—acquire distinct spectra, and Fermi surface correlations have unusual exponents. The luttinger liquids comprise most interacting 1‐dimensional systems, and some higher‐dimensional systems in which, as in the Hubbard model, the band spectrum is bounded above. All higher‐dimensional systems with true Mott‐Hubbard gaps and an upper Hubbard band, including most 2d Hubbard models, are Luttinger liquids. We summarize the experimental evidence in favor of the 2d Hubbard model for highTcsuperconductors and the constraints pointing towards its non‐Fermi liquid nature. We describe progress towards explaining normal state and superconducting properties and elucidating the highTcmechanism.

ISSN:0094-243X    

DOI:10.1063/1.39744

出版商:AIP    

年代:1990

数据来源: AIP

ISSN:0094-243X    

DOI:10.1063/1.39745

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

This presentation discusses the validity of the concept that the conductivity and the other metallic properties in the new high‐Tcoxides arise from a doping process. If the concept is correct, the model based on the electron spectrum constructed from a periodic array of localized centers hybridized with a number of itinerant bands (the periodic Anderson model) provides results which may be relevant to the new materials and their properties.

ISSN:0094-243X    

DOI:10.1063/1.39713

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We report observation of hexatic order in Abrikosov flux lattices in very clean crystals of the highTcsuperconductor Bi2.1Sr1.9Ca0.9Cu2O8+&dgr;(BSCCO). Our experiments consist ofin situmagnetic decoration of the flux lattice at 4.2 K. Analysis of the decoration images shows that the positional order decays exponentially with a correlation length of a few lattice constants while the orientational order persists for hundreds of lattice constants and decays algebraically with an exponent &eegr;6=0.06±0.01. Our results confirm recent theoretical speculation that the positional order should be far more sensitive to disorder than the orientational order and that the low temperature ordered phase of the flux lines in these systems might be an hexatic glass.

ISSN:0094-243X    

DOI:10.1063/1.39714

出版商:AIP    

年代:1990

数据来源: AIP