Superconducting explanations

The gap in superconductivity between the fifth and sixth groups of the periodic table, discovered by Matthias,24 is seen to correspond to the transition from crest to trough superconductivity. It does not require for its explanation the assumption20- 25 that there are mechanisms of superconductivity other than the electron-phonon interaction. 

When the BETS donor replaces the BEDT-TTF electron donor molecule during the electrocrystallization process, crystals of KL-(BETS)2Ag(CF3)4(TCE) have been prepared [29] and structurally characterized. Replacement of the inner sulfur atoms of BEDT-TTF with selenium results in a slight expansion of the unit cell and prevents the stabilization of a superconducting state above 1.2 K. Disorder in one of the BETS ethylene endgroups has been offered as a possible explanation. 

In essence, this model states that initiation occurs when a shocked region of LE becomes thermally superconductive (as a result of rising temp due to partial decompn of the shocked LE) and a heat pulse flashes across the shocked LE and catches up with the original shock front. As described in the article on Heatpulse (p H59-L), alternate explanations are possible for some of the observations that Cook considers to be the main experimental support for his heat pulse . Similarly, Dremin et al (Ref 17) have suggested an alternate ex-... 

An unusual feature of the cuprate superconductors is the anomalous suppression of superconductivity in La2 Ba Cu04 and related phases when the hole concentration X is near 1/8. A possible explanation is a dynamical modulation of spin and charge giving antiferromagnetic stripes of copper spins periodically separated from the domains of holes. Neutron-diffraction evidence has been presented in the case of Laj g Nd() Sr CuO (x = 0.12) which is a static analogue of the dynamical stripe model (Tranquada et al., 1995). It appears that spatial modulations of spin and charge density are related to the superconductivity in these oxides. 

In this paper, we investigate our two-band model for the explanation the multi-gap superconductivity of MgB2. We apply the model to an electron-phonon mechanism for the traditional BCS method, an electron-electron interaction mechanism for high- Tc superconductivity, and a cooperative mechanism in relation to multi-band superconductivity. 

Kamerlingh Onnes, at the University of Leiden, discovered superconductivity in 1911. He found that the resistance of some metallic wires became zero at very low temperature it did not just approach zero, there was no dissipation of heat. At that time his laboratory was the only one equipped for studies at the temperature of liquid He (bp 4.1 K). Theoretical explanations of the phenomenon did not appear until the work of John Bardeen, Leon Cooper, and Robert Schrieffer in 1957. They received the Nobel Prize in Physics in 1972. The expense and difficulty of applying superconductivity to practical problems limits the applications. Nevertheless, superconductor magnets of very high field are now widely used in NMR in chemistry and the medical diagnostic applications of NMR called MRI (magnetic resonance imaging—they wanted to avoid the word "nuclear ). 

R. C. Haddon. I think so. The explanation that I have mentioned seems to be fairly successful in accounting for the result. It is based on vibrations, even though they are molecular vibrations. As far as I know, there is no accepted theory of superconductivity in ceramics. In fact, that is one of the uses we can point to for C60 superconductors. I think that, in the end, these will be among the best understood of the superconductors. 

I shall not elaborate on the triviality of this explanation but only to ask one question to the author who wrote this article (since the referee forgot to ask). If the BCS theory was correct, why then Sc, and Y, metallic elements which all have only one isotope and also have a high N(e)r (electron density of states at the Fermi level), the requirement imposed for a high Tc by the BCS theory, are not superconductors Of course, they can explain somehow. But, in the Covalon conduction theory there is no need for an explanation or no elaborate mathematical equation necessary. It can be easily understood in terms of their atomic orbital. The answer in Covalon conduction theory is simply that both elements are III-A elements in the periodic chart and their atomic orbital are not conducive in forming conjugated covalent bonds, therefore there is no Covalon conduction to lead them to superconductivity. 

Calandra, M. and F. Mauri. 2006. Theoretical explanation of superconductivity in CaC6. Phys. Rev. Lett. 96 237002-1-4. 

Within weeks of the confirmation of the discovery of high temperature superconductivity in the cuprates by Bednorz and Muller, Anderson[l] suggested an explanation of the phenomena and called it resonating valence bonds (RVB). Despite an enormous theoretical effort by the international scientific community, systematic or consistent theoretical results have been hard to obtain on this idea for the model proposed by Anderson for the cuprates. When some specific predictions were made based on the general ideas or approximate calculations, experiments did not conform. 

Science Foundation. Several large superconducting instruments were being installed when a government safety inspector appeared and demanded to know what provisions were being made to handle the nuclear waste produced by these instruments. Assume you are the manager of the NMR center, and offer an explanation that could be understood by a nonscientist. 

Not too many theories have been formulated from this point of view and some of the more interesting cases are at the speculative stage of development. Even so, it is remarkable how some of the most enigmatic of natural phenomena have no convincing explanation apart from broken-symmetry theories. Included are the initiation or nucleation of phase transitions, superconductivity (T4.5.1), the arrow of time (entropy) and the cosmic imbalance between matter and antimatter. The beauty of the world, indeed seems to lie in approximate symmetries. 

We have discussed the characteristics of a number of copper oxide superconductors, a group of materials that have many properties in common. These shared properties might well provide the key to the development of an explanation of the mechanism of high-temperature superconductivity. The most important common features are ... 

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