Muller, and Bednorz

In a previous section, it was shown how the substitution of Y3+ for Las+ was an important step towards the formation of new compounds for superconductivity research. This substitution attempt led to the discovery of the 1-2-3 (or 90 K) superconducting compound. Substitutions similar to that proposed by Muller and Bednorz are now outlined. The type of chemical substitutions, based on atomic radii, which were proposed for La2Cu04, are presented in the following Table 11. 

Muller and Bednorz shared the 1987 Nobel Prize in physics for their discovery of superconducting laBa GUjO. ... 

Superconductors are materials that have the ability to conduct electricity without resistance below a critical temperature above absolute zero. The phenomenon of superconductivity was first seen in mercury at liquid helium temperatures. Great interest developed in this area in the late 1980s, when Muller and Bednorz discovered that even ceramic-like materials can exhibit superconductivity. C. W. Chu subsequently found yttrium barium copper oxide (YBCO) to be superconducting above liquid nitrogen temperatures. Indeed, various books are devoted to this subject. > In the following subsections we highlight representative force field applications that have aided the understanding of static and dynamic properties of superconductors. 

K. Alex Muller and J. Georg Bednorz, "The Discovery Of A Class Of High-temperature Superconductors , Science, 237 1133-1139 (1987). 

Since 1911, scientists have been searching for materials that superconduct at higher temperatures, and more than 6000 superconductors are now known. Until 1986, however, the record value of Tc was only 23.2 K (for the compound Nb3Ge). The situation changed dramatically in 1986 when K. Alex Muller and J. Georg Bednorz of the IBM Zurich Research Laboratory reported a Tc of 35 K for the non-stoichiometric barium lanthanum copper oxide BavLa2-.vCu04, where x has a... 

In 1986, IBM researchers K. Alex Muller and Georg Bednorz paved the path to superconductivity at slightly higher temperatures using a ceramic alloy as a medium. Shortly thereafter, a team led by University of Houston physicist Paul Chu created a ceramic capable of superconductivity at temperatures high enough to encourage true commercialization. 

The discoveries that generated the extensive news coverage in early 1987 were the initial report of superconductivity in the lanthanum compound by Bednorz and Muller,and the observation of superconductivity in the compound YBa2Cu307 at 92-94 K, well above the boihng point (77 K) of liquid nitrogen. The latter result was the outcome of a collaboration between the research groups of C. W. Chu of the University of Houston and M. K. Wu of the University of Alabama. 

IBM researchers Alex Muller and Georg Bednorz make a ceramic compound of lanthanum, barium, copper, and oxygen that superconducts at 35° K. 

Muller, K. Alex, and Bednorz, J. Georg (1987). The Discovery of a Class of High-Temperamre Superconductors. Science 237 1,133-1,139. 

In January 1986, K. Alex Muller and J. Georg Bednorz, scientists at an IBM laboratory in Switzerland, discovered that a barium—Ianthanum-liquid helium. This discovery provoked a flurry of activity that quickly resulted in a substance that became superconducting at 90 K. LaBa2CujO was then... 

In 1986, Bednorz and Muller, and somewhat later Chu and Wu et al, discovered superconductivity at considerably higher temperatnres than 25 K in cuprates. The latter reached 92 K in the cuprate YBa2Cu307 (Figure 17.3), which physicists referred to as 123 or YBCO. Twenty-five years later, there is still no accepted improvement of the BCS model that could explain high T supercondnctivity. Some scientists even believe that there is a new kind of superconductivity where pair formation is due to other interactions than phonon interactions. 

Because of the numerous bogus reports of high-temperature superconductivity before 1986, Karl Muller and J. Georg Bednorz were extremely cautious in revealing their discovery, and their tentative announcement was so modest that their paper initially aroused little interest. 

Student Annotation Allex Muller and Georg Bednorz were awarded the 1987 Nobel Prize in Physics "for their important breakthrough in the discovery of superconductivity in ceramic materials."... 

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