What is graphene?

Want to win a Nobel prize while discovering a material that’s cheap, transparent, flexible but resistent, and an astonishing electric conductor? Grab a pencil and a roll of adhesive tape. I’m serious.

Pencil leads are made of graphite, a form of carbon made of layers of atoms organized in hexagonal cells, like a bee hive. Atoms on the same layer stick together tightly, but are much more loosely attached to the next layer. So, when we write, a few layers peel off the tip and go to the paper.

CC-BY-SA AlexanderAlUS via commons

The sci-fi tech that lead to the discovery of graphene
credit: WikimediaImages/pixabay

If graphite sounds like graphene, it’s because they’re pretty much the same thing. Andre Geim and Konstan Novoselov (who won the Nobel prize for their discovery) created graphene for the first time by repeatedly sticking tape to graphite and ripping it off. Every time a few layers would stick to the tape, until what was left was a single atom thick.

Because it’s so thin, graphene has only the properties of the carbon layer. Without interference from the other layers, it doesn’t behave like a pencil’s graphite anymore. Instead, it supercharges its properties.

For example, each atom is somewhat willing to part with four of its electrons. In a graphene sheet, the atom only has three neighbors to share electrons with, so one is pretty much free to leave and roam around. This makes graphene extremely conductive. If the electrons were busy sticking to other layers (as in graphite) the material would conduct less.

Being so thin, graphene is rather transparent, and very light. But it’s also spectacularly strong (more than steel), thanks to the strong bonds between its atoms.

Thanks to its fantastic properties, graphene is the protagonist of countless works in material science. Electronic devices cannot ask for better than a very conductive material, that doesn’t break and can be used for touch screens.

Making big enough sheets isn’t easy, though, so it still takes a while to have industrial-scale use of graphene.

And if you still want that Nobel prize, I’m afraid the sticky tape and pencil way is taken.

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Cover photo: Graphene, CC-BY-NC-SA Martin Griffiths/flickr

Theoretical donuts and quantum computers: the Nobel prize 2016

So it wasn’t gravitational waves after all: the Nobel prize for physics went to David Thouless, Duncan Haldane and Michael Kosterlitz. That’s the easy part. The motivation needs a little unpacking:

For theoretical discoveries of topological phase transitions and topological phases of matter.

We all know and love a few phases of matter: solid, liquid and gas (maybe plasma if you want to get kinky). Phase transitions happen when, changing temperature or other conditions, matter goes from one form to the other, like melting ice. But there are more phases and more transitions transitions, some involving electrical and magnetic properties of materials.

Thouless, Haldane and Kosterlitz

David Thouless, Duncan Haldane and Michael Kosterlitz

That’s what the newly-minted Nobel laureates where after. They studied the sudden changes in electrical conductance—the efficiency in carrying electric currents—that some cold materials (I mean -270-odd Celsius) undergo when the temperature changes slightly. This effect is impossible to deal with using quantum mechanics, because it has to do with collective behavior of electrons rather than single ones.

Instead, Thouless, Haldane and Kosterlitz used topology. Topology is the branch of math that deals with properties that stay the same when stretching, twisting and bending stuff, but not puncturing, ripping or gluing it. Topologically speaking, a donut is the same as a pipe—we can turn one into the other—but is different from a ball, because we’d have to sew its hole shut.

Topological features like the number of holes must come in integer numbers: there’s no such thing as a half-hole! So they change in jumps, like that weird conductance. So the scientists theorized that topological transformtions (though not really holes appearing), were behind it.

topology_steps

Steppy changes in topology cause sudden changes in conductance. There are no actual holes involved in the process, though! Holes appearing are just one example of topological changes. Credit: Johan Jarnestad/The Royal Swedish Academy of Sciences

The unusual part of the award is that the discoveries haven’t been applied quite yet: they are purely theoretical. However, they opened the floodgates for the research on materials that exploit these properties. For one, topological materials are an avenue towards the dream of building a quantum computer. During the press conference, Haldane explained that topology could protect the fragile signals in quantum computers from disruption due to impurities in the material itself.

Cover photo: CC0 Thomas Kelley via unsplash.com

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What if gravitational waves don’t win the Nobel prize?

Most predictions for the winners of this years Nobel prize for physics point to the biggest piece of science news we’ve had: gravitational waves. I’ll go out on a limb and say that I’m not convinced they will.

Don’t get me wrong: I’m a great fan of team LIGO’s work, too. The discovery of gravitational waves was incredible, but so was the Higgs boson. LIGO is an astonishing feat of science and engineering, but so was the LHC. We expected to find gravitational waves as much (if not more) than we expected the boson. However, that Nobel prize was awarded only to Higgs and Englert, who formulated the theory. In the case of gravitational waves, it would be Einstein, who is ineligible being… you know… dead.

I firmly believe the LIGO team will get their gold: they opened a whole new window on the universe. As soon as we find something new in that window, I think, they will jump to the top of the list. That time will come, just not yet.

Who else can win if LIGO doesn’t? Thomson Reuters has an effective citation-based system. Other than LIGO people—suggests Marvin L. Cohen on one side, and Celso Grebogi, Edward Ott and James A. Yorke on the other (you can find the infographic here, and see they missed the medicine prize already). The first worked on a method to study semiconductor properties. The latter group worked on chaos theory. Should they win, we’ll go into more detail of what these discoveries are and mean on next Friday’s post.

Personally, my buck is somewhere else: I’m going with exoplanets.

Still, it’s all speculation. Nobel winners do science, unlike people that attempt these predictions.

Cover photo: CC0 nvodicka, via pixabay.com