New Superconductor Theory May Revolutionize Electrical Engineering 92
An anonymous reader writes "High-temperature superconductors exhibit a frustratingly varied catalog of odd behavior, such as electrons that arrange themselves into stripes or refuse to arrange themselves symmetrically around atoms. Now two physicists propose that such behaviors – and superconductivity itself – can all be traced to a single starting point, and they explain why there are so many variations. Most subatomic particles have a tiny magnetic field – a property physicists call 'spin' – and electrical resistance happens when the fields of electrons carrying current interact with those of surrounding atoms. Two electrons can join like two bar magnets, the north pole of one clamping to the south pole of the other, and this 'Cooper pair' is magnetically neutral and can move without resistance. Lee and Davis propose that this 'antiferromagnetic' interaction is the universal cause not only for superconductivity but also for all the observed intertwined ordering. They show how their 'unified' theory can predict the phenomena observed in copper-based, iron-based and so-called 'heavy fermion' materials."
Journal Article (Score:5, Informative)
Would it kill them to link to the original paper? It's not even paywalled:
http://www.pnas.org/content/110/44/17623.full.pdf+html?sid=5925a7b2-3efe-4a21-99f9-0e448cd3a7cf [pnas.org]
a better summary (Score:5, Informative)
(Why was a poorly written press release linked instead of the actual paper?)
This paper shows how you can start with an extremely simple theory of electron interaction and build up to some very complicated, realistic superconducting behaviors. When varying the material properties of high temperature superconductors, you always see an antiferromagnetic material type near the superconducting material composition. For many years condensed matter physicists have suspected that this was more than a coincidence and that high temperature superconductors work because of finely tuned antiferromagnetic interactions between electrons. Although this paper simplifies electron interactions considerably (come on, we're physicists, simplification is what we do), it does fill in some of the larger holes in that theory and is an important step toward understanding the physics behind the phenomenological high temperature superconductivity models.
Re:the question is (Score:5, Informative)
You do not need 2K for supraconduction: there is at least one class of supraconductor ceramics that works at temperatures as high as 135K and another (YBCO) that works at 92K which makes them relatively simple to cool by simply using liquid nitrogen. Most of the others operate in the 25-55K range.
Re:Its kinda obvious (Score:5, Informative)
Too bad China has the monopoly on rare earths.
They're not actually rare. China has a monopoly mainly by being a very cheap producer of something that requires a lot of messy processing to make; everyone else is happy to let them have a monopoly because it's expensive to do otherwise, not because they actually control all possible sources.
Re:Spin a magnetic field? (Score:2, Informative)
You and whoever has been modding you up should actually go look up quantum mechanics and the hydrogen atom, Maybe this more general article on angular momentum [wikipedia.org] will be helpful. And then maybe look up what those four quantum numbers are used to describe the state of an electron in a hydrogen like atom:
n - principle quantum number - comes from the radial part of the solution of the Schroedinger equation, determining which shell the electron is in.
l - orbital quantum number - so named because it is the magnitude of the orbital angular momentum
m - magnetic quantum number - which is quantization of the projection of orbital angular momentum along an axis determined by a magnetic field
s - spin quantum number - indicating the direction the quanta of intrinsic spin of the election is pointed in, with or against the magnetic field.
None of these are the total angular momentum, which would be the vector sum of the spin and orbital angular momentum: J = L + S, and includes a total angular momentum quantum number j=l+s.