New calculations reveal that the p-doping should graphane superconduct at 90 K, making possible a whole new generation of devices cooled by liquid nitrogen.
There is a problem with high-temperature superconductors. More than two decades ago it was discovered that certain copper oxides can superconduct at temperatures above 30 K.
Those years were full of promises, hyperbole and fervent research. Physicists now know that copper oxides superconduct in a completely differently from conventional BCS supercondcutores (by Bardeen, Cooper and Schrieffer, who developed the theory that lies beneath them.) And, again, no one agrees on precisely what the new mechanism. He has not even created a supreconductor that is useful at room temperature, ie above the temperature of liquid nitrogen.
Even with the resurgence of enthusiasm following the discovery last year that superconducía magnesium diboride at high temperatures, probably in the same way that the BCS from the old school, soon gave way to unease when physicists discovered that they were unable to build on this progress to create better superconductors. It is tempting to think that superconductors will never exceed the barrier of liquid nitrogen.
But today the hope is recovered thanks to a fascinating set of calculations performed by Gianluca Savini, University of Cambridge in the UK and a couple colleagues. Calculated the properties of p-doped graphane from its basic principles and say it should superconduct at the warm temperature of 90K or more, well within the range of liquid nitrogen cooling.
Moreover, the p-doped graphane should superconduct in the same way they do the old BCS superconductors. This is curious because everyone believes that the BCS superconductivity can not operate at high temperatures.
The reason is the energy of the interaction between superconducting electrons and the surrounding material. In ordinary BCS superconductors it is believed to be of only a dozen Mevs. In oxides Copper, however, these interactions have an energy of hundreds of Mevs. This difference is what makes physicists believe they will never work BCS superconductors at the temperature of the copper oxides.
And although the discovery of superconducting magnesium diboride challenges that idea - the energy of these interactions in MgB2 is much higher. Appear to be three factors combine to make this possible, say Savini and company. The first is the characteristic energy of phonons in MgB2 which is due to the extension of the bonds and plays an important part in helping superconducotres through the structure. Second is the density states of the electrons in the material and finally point out the balance between electron-phonon coupling and repulsive electron-electron interaction in MgB2.
Could it be possible to find materials in which these amounts can be handled even more? You bet it does. Savini and his colleagues observed that the p-doped diamond has two of these features but superconducts only 4K.
however, estimate the p-doped graphane fits perfectly and should superconduct at 90K in the form of the old BCS. Moreover, they say there are clues that the nanowires of p-doped diamond may have similar properties.
The implications of this are staggering. First is the possibility of useful superconducting devices cooled by liquid nitrogen only. Finally!
But there are other more exotic involvement: building doors similar to those of a transistor from graphane doped in different ways, it should be possible to create devices that can be turned on and off the superconductivity. This will enable an entirely new class of switches.
Before that, however, someone has to do graphane p-doped. It will be difficult. Graphane himself barely first produced last year at the University of Manchester. Would be fun to follow the race to create and test the p-doped version.
Source: http://wiki.taringa.net/posts/info/4776408/El-grafano-dopado-deber% C3% ADa-superconduct-a-90K.html
Mario Pedraza
Solid State Electronics
Section 2.
