摘要:

AbstractDuring investigations of the magnetic flux dynamics in thin superconducting YBa2Cu3O7−xfilms we have observed the spontaneous formation of a damage in the film, apparently induced by the applied magnetic field of 0.1T. The damage developed within less than 40 ms (the time resolution of the experiment) and showed up in the magnetiooptically recorded image of the flux above the sample as a path for massive flux penetration. A subsequent analysis revealed a 1 μm wide gap in the YBa2Cu3O7−xfilm which had developed over a major portion of the 1 · 1 cm2sample. It is suggested that the film locally melted as a result of an instability of the superconductor in the critical

ISSN:0003-3804    

DOI:10.1002/andp.19925040402

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractAtomic resolution images of layered transition metal‐dichalcogenide ReS2single‐crystals (n‐type semiconductor) were obtained using a scanning tunneling microscope with a positive tip. In most cases only unresolved clusters of four rhenium atoms could be seen. Occasional images with higher resolution showed that these bright structures consist of four separated atoms. The symmetry of the imaged atoms is identical to that of the rhenium sublattice but not to that of the sulfur atoms. We conclude therefore that the main contribution to the tunneling current is due to the rhenium atoms, although the sulfur atoms are placed by about 0.15 nm closer to the tip. Thus for our positive bias of the tip the tunneling electrons originate from occupied rhenium states in the valence band of the semicond

ISSN:0003-3804    

DOI:10.1002/andp.19925040403

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractA linear response formalism is developed which is based on density functional theory within the local density approximation, but which is now corrected for its spurious self‐interaction errors, in the way originally proposed by Perdew and Zunger for ground state calculations. The original formulation is extended to incorporate self‐interaction corrections in the scrrening terms. The general formalism is then applied to the calculation of the static and dynamic response of the metal clusters {Na8, Na9+}, {Na20, Na 21+} and {Na40Na 41+} within the jellium model. Comparison with experimental data and with other theoretical calculations indicates that the present formalism accounts for the overall (and most of the fine) features of the photoabsorption spectrum of these systems, providing a systematic improvement with respect to previous approaches. The remaining discrepancies are rationalized in terms of the effects to be expected by correctly accounting for the discrete structure of the ioni

ISSN:0003-3804    

DOI:10.1002/andp.19925040404

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractWe have studied the competition experimentally observed between fission and neutral atom evaporation, as dissociation channels of excited doubly charged sodium clusters, using the Density Functional Theory and the jellium model. The fission barrier has been obtained from an Extended Thomas‐Fermi calculation including density gradient corrections to the kinetic energy of the electronic cloud. We discuss the influence of the coefficient of the density gradient term on the barrier heigh

ISSN:0003-3804    

DOI:10.1002/andp.19925040405

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractThe Grüneisen relation Γ = αpKTV/Cνhas been integrated with respect toTat constant volume. This leads to a potentialE(V) with the two exponents Γ =m/3 and δ =n/3. The Grüneisen constant Γ is the exponent of the repulsive term. The exponent δ of the attractive term may be determined from heat capacity, thermal expansion and cohesive energy, δ =Cp/αp/ϵc.The pressure coefficient of the bulk modulus of anm‐npotentialE(V) is given byK0′ =m/3 +n/3 + 2. According to the calculations above we obtainK0′ from thermophysical data byK0′ = Γ + δ + 2 = αpKTV/Cν+Cp/αp/ϵc+ 2, withK0′ = 4‐5 for alkali metals,K0′ = 5.2‐6.2 for transition metals andK0′ = 7‐8 for solid rare gas crystals. This is in g

ISSN:0003-3804    

DOI:10.1002/andp.19925040406

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractWe have studied the influence of bond‐ and site‐type impurities on the ground state properties of one‐dimensional Peierls systems. Using a functional integral formalism with both commuting and anticommuting variables we have calculated the averaged Green's function which determines the electronic density of states and localization length (Thouless formula). Some limiting cases can be solved analytically. To apply our model to doped polymers we derive the connection between doping concentration and disorder strengthsDj. For illustration we present the results with parameters appropriate for polyacet

ISSN:0003-3804    

DOI:10.1002/andp.19925040407

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractA model of layered superconducting structure consisting of alternating anisotropic superconducting layersS1andS2with different transition temperatures is considered. It is shown that due to competition between two origins of anisotropy ‐ effective‐mass anisotropy of individual layers and proximity‐induced anisotropy the effective anisotropy of the whole system signficiantly varies temperature. The components of the effective‐mass tensormc(along the anisotropy axis) andma(perpendicular to the anisotropy axis) strongly depend upon temperature. This may lead to transition between layered (mc>ma) and quasi one‐dimensional (mc

ISSN:0003-3804    

DOI:10.1002/andp.19925040408

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractWe construct and discusss explicitly time dependent integrals of the motion of non‐autonomous quantum systems. Such integrals may exist even when the classical limit of the dynamics is non‐integra

ISSN:0003-3804    

DOI:10.1002/andp.19925040409

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY

ISSN:0003-3804    

DOI:10.1002/andp.19925040401

出版商:WILEY‐VCH Verlag    

年代:1992

数据来源: WILEY