Urban legend has it that American engineers spent more than a million dollars inventing an 'astronaut pen' that could work in space, while the Russians simply used a pencil. True or not, the tale shows that the best solutions can sometimes be found in mundane objects. And, indeed, that they can be found in pencils.

Pencils contain graphite, a form of carbon in which atoms are ordered in thin sheets stacked regularly on top of each other. The interaction between these sheets is small, so layers of graphite rub off easily, for example when a pencil draws a line on paper.

Not satisfied with such an obvious, practical use, physicists have long been fascinated by the electronic properties of a single sheet of graphite, called graphene. Graphene is unlike any other material because electrons within it can behave as massless particles, which means they can mimic relativistic physics. Exotic effects that normally require huge particle accelerators might therefore be observed in a simple device — if only it were possible to rub off one, and only one, sheet of graphene.

Despite concerted efforts, this proved problematic. In 2004, researchers at the University of Manchester, UK, finally isolated graphene when they peered through a conventional optical microscope at flakes of graphite that they had simply ripped off from a larger piece with sticky tape (K. S. Novoselov et al. Science 306, 666–669; 2004). Graphene, being a layer just one atom thick, is transparent to light. But, as the picture here shows, there is just enough contrast from the thickness variation in a graphite shaving to locate the graphene layer under the microscope (here, the faint, semi-transparent region on the right, indicated by an arrow).

The image was obtained by Hubert Heersche and colleagues, who in this week's issue describe an experiment in which they attached a graphene sheet to two superconducting electrodes (H. B. Heersche et al. Nature 446, 56–59; 2007). Previous experiments had thrown up the unexpected finding that graphene has a small electrical conductivity even in the absence of mobile charge carriers.


Heersche et al. add to the surprise by showing that the same holds true for a superconducting current. Moreover, it was not at all clear that a supercurrent could flow in graphene. As it turns out, not only does a conventional electron supercurrent flow, but so does one consisting of holes, which carry positive charge.

This experiment shows yet again that novel and surprising effects can be observed in simple materials — good news for those who don't have a million dollars to spend on discovering something new.