ISSN:0031-9228    

DOI:10.1063/1.2810130

出版商:AIP    

年代:1991

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2810131

出版商:AIP    

年代:1991

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2810132

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We expect light to travel through a medium at a rate given by the speed of light in a vacuum divided by the average index of refraction of the material. But a recent experiment performed in the Netherlands indicates that in some strongly scattering materials it may actually take light five to ten times longer to traverse a sample than one would expect from this simple formula for the phase velocity. It appears that the light resonates for a while with the dielectric microspheres of which the material is made so the light takes longer to travel through the sample. This result challenges some assumptions made in the analysis of data from light scattering experiments, especially searches for localized light.

ISSN:0031-9228    

DOI:10.1063/1.2810133

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

One can argue that superconductivity in “the oxides” was discovered in 1964, 1986 or 1987, depending on which oxide is chosen: the first to show superconductivity at any temperature, the first with aTcgreater than 20 K or the first with aTcgreater than 77 K. For many of us in the field, the time we remember is probably early December 1986, when experimenters from the University of Tokyo announced at the Materials Research Society meeting in Boston that they had confirmed the earlier findings of Georg Bednorz and Alex Mu¨ller at IBM in Zurich. There followed a frenetic period of a year or so that was unique in the history of science, with the American Physical Society meeting of March 1987 representing its peak of intensity (or hype, depending on one's point of view), although a close second must have been the Washington gathering where President Reagan gave the plenary talk.

ISSN:0031-9228    

DOI:10.1063/1.881302

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

From the discovery of oxide superconductors in 1964, there were frequent indications that these materials are metastable. This lack of thermodynamic stability has now become one of the predominant issues in the synthesis of the high‐temperature superconductors. Once prepared, metastable superconductors possess sufficient kinetic stability that we generally need have no concern that they will decompose into more stable phases that are not superconducting. Nonetheless, our understanding of the issues relating to the stability of the known superconductors greatly influences our approaches to synthesizing them. Furthermore, understanding the relationship between instabilities and the mechanism of high‐Tcsuperconductivity could be the key to the synthesis of superconductors with even higher critical temperatures.

ISSN:0031-9228    

DOI:10.1063/1.881303

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Few superconducting materials have presented us with the structural elegance and complexity displayed by the recently discovered high‐Tccopper oxides. The structures of these materials, consisting of metal‐oxygen layers stacked in a variety of sequences, with the metal atoms often in unusual coordinations, are interesting in their own right. More importantly, our present understanding of the properties of the oxide superconductors depends heavily on a knowledge of their structures.

ISSN:0031-9228    

DOI:10.1063/1.881304

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Four years of intensive research following J. Georg Bednorz and K. Alex Mu¨ller's discovery of high‐temperature superconductors has produced about 18 000 publications. An overview of all physical properties is thus beyond the scope of this article, so I will focus on a few topics that are widely perceived to hold the key to understanding these fascinating compounds.

ISSN:0031-9228    

DOI:10.1063/1.881260

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Anderson: The consensus is that there is absolutely no consensus on the theory of high‐Tcsuperconductivity. I suppose that, in a way, this is true. One can find groups working with some level of conviction on almost every hypothesis, and there are groups from very diverse backgrounds (such as quantum chemistry, electronic structure and many‐body physics) working on the problem, groups that have very little meaningful communication with each other. Looked at relative to this scientific Tower of Babel, I suspect you and I are practically speaking the same language. Would you agree?

ISSN:0031-9228    

DOI:10.1063/1.881261

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A worldwide effort to develop high‐temperature‐superconductor thin films and electronic devices began within weeks of the initial discovery in early 1987 of superconductivity above liquid‐nitrogen temperature. The ensuing period has seen remarkable progress, spurred by innovations in deposition technology, materials characterization and device design. Prospects for practical electronic applications of superconductivity have driven the development of high‐temperature‐superconductor thin‐film technology at an unprecedented pace. After five years researchers in the field have surmounted many of the initial hurdles in developing the new materials, and they are now working toward the first practical implementations of high‐temperature‐superconductor electronic technology.

ISSN:0031-9228    

DOI:10.1063/1.881262

出版商:AIP    

年代:1991

数据来源: AIP