摘要:

By comparing the properties of superfluid4He with the copper oxide superconductors, a model is given to explain the disappearance of superconductivity for high levels of doping.

ISSN:0950-0839    

DOI:10.1080/09500839308242420

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The superconducting instability in a non-Fermi liquid in dimensionsd> 1 is considered. For a particular form of the single particle spectral function with homogeneous scalingA(λk, λ ω) = λαA(k, ω) it is shown that the pair susceptibility is also a scaling function of temperature with power defined by α. We find three different regimes depending on the scaling constant. Bardeen-Cooper-Schrieffer result is recovered for α = − 1 and it corresponds to a marginal scaling of the coupling constant. For α > − 1 the superconducting transition happens above some critical coupling. In the opposite case of α < − 1 for any fixed coupling the system undergoes a transition at low temperatures. Possible implications for theories of high-Tcwith a superconducting transition driven by interlayer Josephson tunnelling are discussed.

ISSN:0950-0839    

DOI:10.1080/09500839308242421

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A study of helium bubble growth by positron lifetime measurements made on helium-implanted palladium (100at.p.p.m. He) is reported. The temperature of formation of stable bubbles which retain helium in post-implantation annealing is identified to be 750±20K. The average bubble radius, bubble concentration and helium pressure in the bubble are obtained from an analysis of experimental data. The variation in the deduced bubble parameters in the annealing temperature range 973–1473 K is compared with that calculated on the basis of surface diffusion controlled migration and coalescence model, allowing for pressure effects as suggested by Mikhlin in 1979. The comparison is found to be satisfactory. The observed results are explained as due to suppression of bubble mobility at high internal pressures and subsequent enhancement of the mobility on pressure relaxation.

ISSN:0950-0839    

DOI:10.1080/09500839308242422

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

We have used the equation-of-motion method to simulate the motion of wave packets representing electrons in the presence of a potential gradient for both crystalline and amorphous silicon. This is used to determine the sign of the electron effective mass for various energies in the valence and conduction band. There is a close correspondence between the crystalline and amorphous results and there is therefore no indication of the double-sign anomaly of the Hall coefficient.

ISSN:0950-0839    

DOI:10.1080/09500839308242423

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor