摘要:

Investigations of short range lattice fluctuations and anharmonic lattice modulation of theCuO2plane, in theBi2Sr2CaCu2O8+&dgr;superconductors, with high momentum resolution extended x-ray fine structure (EXAFS) and x-ray diffraction (XRD), show the coexistence of the polaronic and itinerant charges ordered in lattice-charge stripes with the wavevectorqlatticeand a strong second harmonic content with2qlattice.The study of momentum distribution of spectral weight around the Fermi level, measured by angle resolved photoemission (ARPES), reveals a large suppression of spectral weight due to coupling of charge carriers with joint incommensurate charge density wave atq(−0.4&pgr;,0.4&pgr;)−2qlatticein the diagonal direction and the spin density wave at G (&pgr;, &pgr;) in the direction of the stripes. The lattice-charge stripes and their implication on the electronic spectral weight are briefly discussed. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.59614

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

An overview is presented of some evidence that the charge-reservoirs, not the cuprate-planes, are the loci of the primary superconductivity in high-temperature superconductors. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.59615

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

The detection of granular superconductivity in Pr222Nb-10 leads to the conclusion thatR2−zCezCuO4(R21-4) compounds andR2−zCezSr2Cu2NbO10(R222Nb-10) compounds both superconduct forR=Pr.The fact that Gd21-4 does not superconduct, but Gd222Nb-10 does, indicates that the superconducting layers are different in the two classes of compounds. Magnetic resonance studies of Gd222Ru-10 and Gd21-4 indicate either that ordered magnetism and superconductivity co-exist in the cuprate-planes or else that the cuprate-planes are not the primary superconducting layers in Gd222Ru-10. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.59616

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

The evidence thatPrBa2Cu3O7is a bulk superconductor is reviewed, together with evidence that the primary superconducting layer involves the charge-reservoirCuOlayer and its neighboringBaOlayers. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.59617

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

We report transverse-field muon spin rotation studies of the magnetic field distribution n(B) in the vortex state of the high temperature superconductorBi2Sr2Ca1Cu2O8+&dgr;(Bi-2212) and present data on three sets of overdoped, nearly optimized and underdoped single crystals which to our best knowledge provide the first evidence that a two-stage melting transition of the vortex matter occurs under equilibrium conditions. In addition, we compare the TF-&mgr;SR results with those from DC-magnetization measurements and magneto-optic experiments on the same crystals. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.59618

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

Key features of antiferromagnetic dynamical correlations in high-TCsuperconductors cuprates are discussed. In underdoped regime, the sharp resonance peak, occurring exclusively in the SC state, in accompanied by a broader contribution located around ∼30 meV which remains aboveTC.Their interplay may induce incommensurate structure in the superconducting state. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.59619

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

Measurements of thermal conductivity (&kgr;) versus temperature and doping for several cuprate superconductors are discussed. Suppressed values of the normal-state &kgr; and the slope change in &kgr; atTc,observed near 1/8 doping in bothYBa2Cu3O6+xand Hg cuprates, are attributed to local lattice distortions and the suppression of the superconducting condensate, respectively. Both phenomena are proposed to arise from small domains of localized planar holes, presumably a manifestation of phase separation. It is suggested that the phase behavior of &kgr; reflects stripe dynamics and the 1/8 doping anomalies stripe pinning by oxygen-vacancy clusters. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.59620

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

Time-resolved optical measurements give information on the quasiparticle relaxation dynamics in YBCO, from which the evolution of the gap with doping and temperature can be systematically deduced. In this paper these optical charge-channel “pseudogap” data are compared with the “pseudogap” obtained from the NMR Knight shiftKs,spin polarized neutron scattering (SPNS) and single particle tunneling measurements. A simple energy level diagram is proposed to explain the different “gap” magnitudes observed by different spectroscopies inYBa2Cu3O7−&dgr;,whereby the spin gap&Dgr;sin NMR and SPNS corresponds to a triplet local pair state, while&Dgr;pin the charge excitation spectrum corresponds to the pair dissociation energy. At optimum doping and in the overdoped state, an additionalT-dependent gap becomes evident, which closes atTc,suggesting a cross-over to a more conventional BCS-like superconductivity scenario. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.59592

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

A brief review is given of the advantages of Andreev scattering in the study of unconventional superconductors such as the cuprates. The use of clean interfaces is made possible by the Point Contact method. Andreev scattering is sensitive to the presence of nodes in the order parameter, which has allowed for an easy check of its symmetry in a large number of cuprates, NdCeCuO and LaSrCuO near optimum doping are two interesting exceptions to a d-wave symmetry. Andreev scattering probes the coherence energy scale in the superconducting state, which has been found to be smaller than the single particle excitation energy gap in the underdoped regime. The implications of this result for current models of the pseudogap are discussed. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.59593

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

Inelastic neutron scattering measurements ofLa1.85Sr0.15CuO4andYBa2Cu3O7show that the dispersion of the high energy LO phonon mode along the (1,0,0) direction is strongly temperature dependent, and at low temperatures develops an anomalous feature indicative of dynamic cell-doubling. The anomaly does not change through superconducting transition and gradually disappears between 50 and 250 K in LSCO. Possible implications are discussed. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.59621

出版商:AIP    

年代:1999

数据来源: AIP