Humble graphene reveals the secrets of the universe

It could even provide the key to world peace, love and understanding, going by the tone of a breathless press release issued earlier this month by the University of Manchester.

Graphene membrane used to measure the fine structure constant

I refer to research on graphene by physicist Andre Geim and his group, together with collaborators at the Universidade do Minho in Portugal. The results of Geim’s experiments have been published online by the journal Science.

This wondrous material is a single-atom thick layer of carbon atoms, which in bulk form is known as graphite. Graphene can be produced by shaving graphite into the thinnest of slices. It can also be grown, although so far with great difficulty. In small quantities it can even be made by rubbing a piece of graphite over a surface pitted with holes, much like writing with a pencil on paper.

Graphene has some amazing structural and electrical properties. If we can work out how to produce the stuff in large volumes, it could in the long term replace silicon in high-performance electronics. Note, however, that while there is plenty of talk in the electronics industry and technology media of the “post silicon” age, much of this is hot air.

Professor Geim and his graduate students Rahul Nair and Peter Blake have for the first time produced large, suspended membranes of graphene that are almost but not quite transparent. In fact they absorb precisely 2.3 percent of visible light transmitted through them, and it seems that this number is highly significant, as I shall explain shortly.

With their graphene membranes the researchers have measured the fundamental physical quantity known as the fine structure constant, which defines the interaction between fast-moving electrical charges and light. The fine structure constant is one of those which if it differed by just a few percent would make the universe unrecognisable and carbon-based life forms impossible. The constant’s numerical value is close to the fraction 1/137.

Theory shows that the fraction of light absorbed by graphene, when divided by the transcendental number π (3.14159… ad infinitum), gives the exact value of the fine structure constant.

Why does this work for graphene and not, say, supermarket cling film? The reason is that the electrons in graphene behave as if they have completely lost their mass. And this means that interactions between electrons and light waves are unaffected by the structure of the material.

It really is a very simple and clever experiment, and quite deserving of a gushing press release. Even if I do mock it. This, by the way, I have done directly with Geim, whose work I have covered in the science media (see here, here and here). I am pleased to report that Andre can take a joke.