Nature's Journal Club

Andre Geim

University of Manchester, UK

Imploding atoms have softened this experimentalist’s teasing views on theoretical physics.

As an experimentalist, I instinctively dislike theory papers. Too many of them seem to be written for the sole purpose of showing off an integral larger than a competitor’s, or to present multiple theories just in case one idea proves right and so is hailed as visionary. I feel even less warmly towards theories that are nigh on impossible to check, such as the supposed precursor to a theory of everything, string theory.

But speaking seriously, even the most obscure predictions can turn out to be spectacularly relevant.

In our lab we have been studying graphene, a material that comprises a single layer of carbon atoms arranged similarly to chicken wire. Because electrons in this material mimic ultra-relativistic particles, it should be possible to observe in their behaviour century-long-predicted phenomena such as the Klein paradox (which concerns how highly energetic electrons tunnel through supposedly impenetrable barriers) and zitterbewegung (jittery movements of relativistic wave-packets).

Several recent theory papers on the physics preprint server arXiv predict another coup for graphene (see A. V. Shytov et al. arXiv:0708.0837; 2007).

According to relativistic quantum theory, atoms containing more than 170 protons cannot exist, because electrons around nuclei with such a large charge would fall into the centre. Nuclear physicists have not come close to creating atoms heavy enough to test this prediction. But the recent theory papers suggest that it should be relatively easy to observe the effect in graphene. This is because electrons in this material interact much more strongly than they do in atoms, so should fall down on charged impurities (standing in for nuclei) rather routinely.

This makes me wonder: could we design condensed-matter systems to test the supposedly non-testable predictions of string theory too?

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