Thursday, 6 August 2009

Electrons, Spinons and Honons

This is interesting.

The paper title "Probing Spin-Charge Separation in a Tomonaga-Luttinger Liquid" by Jompol et al in Science 31 July 2009:
Vol. 325. no. 5940, pp. 597 - 601 sounds almost as interesting as watching paint dry. But if you get beyond the impenetrability of some of the exact, but dense scientific jargon, you find some really neat things happening.

The electron is a fundamental building block of nature and is indivisible in isolation, yet a new experiment has shown that electrons, if crowded into narrow wires, are seen to split apart.

The electron is responsible for carrying electricity in wires and for making magnets. These two properties of magnetism and electric charge are carried by electrons which seem to have no size or shape and are impossible to break apart.

However, what is true about the properties of a single electron does not seem to be the case when electrons are brought together. Instead the like-charged electrons repel each other and need to modify the way they move to avoid getting too close to each other. In ordinary metals this does not usually make much difference to their behaviour. However, if the electrons are put in a very narrow wire the effects are exacerbated as they find it much harder to move past each other.

In 1981, physicist Duncan Haldane conjectured theoretically that under these circumstances and at the lowest temperatures the electrons would always modify the way they behaved so that their magnetism and their charge would separate into two new types of particle called spinons and holons.
The Cambridge physicists, Yodchay Jompol and Chris Ford, clearly saw the distinct signatures of the two new particles as the Birmingham theorists, Tim Silk and Andy Schofield, had predicted.
Neat! Another one of Nature's secrets revealed. OK, now some will say "So what? Of what use is it? Well, read on...

Here's what Dr Chris Ford from the University of Cambridge's Cavendish Laboratory said:
'Quantum wires are widely used to connect up quantum "dots", which may in the future form the basis of a new type of computer, called a quantum computer. Thus understanding their properties may be important for such quantum technologies, as well as helping to develop more complete theories of superconductivity and conduction in solids in general. This could lead to a new computer revolution.'
And from Professor Andy Schofield of the University of Birmingham's School of Physics and Astronomy:
Our ability to control the behaviour of a single electron is responsible for the semiconductor revolution which has led to cheaper computers, iPods and more. Whether we will be able to control these new particles as successfully as we have the single electron remains to be seen. What it does reveal is that bringing electrons together can lead to new properties and even new particles.'
So it's no bigger than the theoretical work that led to computer chips. And how much have electronics affected our lives, after all? Only... completely.


mythusmage said...

Electrons and other leptons are essentially single quarks. That electrons can split into two (maybe more) parts shows that quarks are made up of smaller stuff. Could be strings, or something else entirely. We may have a way to test String Theory.

Lux Mentis said...
This comment has been removed by the author.
Lux Mentis said...

String Theory is probably the one branch of physics desperately seeking a way to justify the vast quantity of research dollars put into it. Testable hypotheses have been few (or none, depending on who you believe).

As to this article itself, it does seem like it has some implications. I recall being taught all through university and college that the electron was essentially an indivisible carrier of charge. The idea that, under some circumstances, you can cause a fairly different specialization of electrons is potentially[1] quite astonishing.

Semiconductors and even some of the attempts at superconductors have more or less hinged on the idea that, under certain circumstances, you can create conditions where behaviours of materials vary from what would normally be expected. If this discovery leads to materials wherein we can specialize the behaviour of electrons, there are all sorts of possibilities.

Quantum computing is in many ways already a game changer. I have heard it suggested that craft of software will be entirely remade by ubiquity and affordability of quantum computers (long term). It promises (as one example) to render conventional encryption methods obsolete. Then again, some quantum tricks may make it possible to have communications which tell you if they have been intercepted. That's only two quick examples from the world of communications where Q-tech promises very different scenarios.

[1] Then again, like many research projects where a discovery is made, the academics often have an incentive to play up its significance. Some fair portion of the time, it turns out that things are harder than expected, the range of things that can actually be engineered from the academic work is more limited than expected, or a subsequent bunch of science proves there are holes in our understanding that render our initial appreciation invalid. Whether this really does make a huge difference will remain to be seen.