neutron said:
Hi,
I read an article about http://sciencenewsdaily.org/story-2387.html. It's been published in the last issue of Nature Materials.
A team of physicists offers a new explanation of the way quantum effects could create some of the strange electronic properties that have been observed in the important class of "heavy fermion" materials. They say it's important to the physics of a broad range of materials, including high-temperature superconductors and carbon nanotubes.
Honestly, I didn't understand much. Can anyone explain it in a simple language?
You should have posted this in the Condensed Matter section of PF, since obviously this subject area was mentioned a few times in the article.
First of all, it may help a bit if you read Piers Coleman's (one of the people cited in that article) essay on Condensed Matter/Many-Body physics as a background information:
http://arxiv.org/abs/cond-mat/0307004
I will not go into quantum criticallity, because unless you have studied many-body physics, then revealing to you what quantum critial points are may cause you to go blind. Spin-charge separation, I can describe a bit since that was one of the stuff I studied when I was a postdoc.
When you describe a particle in solids, such as an electron or a hole, you describe it with a set of quantum "numbers". Two of them are "spin" and "charge" (yes, charge can be a quantized quantum number in terms of "e"). Now, in that article, they mentioned "strongly correlated electrons". In most of our "regular materials", we describe the electrons and other charge carriers as being weakly interacting with each other, i.e. the coulomb repulsion between electrons in a conduction band is neglible and their magnetic properties are non-existence other than to distinguish them as fermions based on their spins.
However, in many such systems, this approximation is no longer valid. The elctrons are tightly confined to a region of the material, and they can no longer ignore the presence of one another. So they are now "strongly correlated". They then exhibit a number of exotic properties. One such property occurs when you confine them to a lower dimension than 3D. In one such cases, in a 1D conductor, a correlated electron system will exhibit what is known as "spin-charge separation". What it means is that if you observe the flow of these particles, it appears that the charge current and the spin current do not flow together. The electron (or charge carrier) appears to have "fractionalized" into two separate entities: one carying the spin (spinon) and the other carying the charge (chargon or holons).
There have been tantalizing evidence for such a phonomenon, such as the violation of the Weideman-Franz law in a couple of experimental results. People are still looking at more materials and experiments to get a more direct and clear evidence for such things.
Zz.
