This house believes …

25 10 2010

A change to Journal Club for this week. Instead of us sitting round discussing the latest results from the literature, we went for a more direct discussion and moved to a full on scientific debate. To this end, we held ‘This house believes … that Graphene is a Superconductor’ with presentations from Kartheek (for) and Amit (against).

Graphene Superconductor Debate

Kartheek presents the case for

Whilst the achievements in graphene are impressive, the description of superconductivity is perhaps a bit beyond the evidence. There is plenty of evidence which supports the ability of Copper pairs to travel between two superconducting contacts and simulations which predict that FLG with odd numbers of layers should show diamagnetism (which interestingly shows an increase in magnetic moment with increasing numbers of layers …), but nothing that shows direct evidence of superconductivity. In the case against, Amit showed that in order for a type I superconductivity (which follows BCS theory) a high electron – phonon interaction is required and that is not observed in graphene. The other issue revolves around the reports that show a ‘superconducting transition’ in resistivity when the material is cooled, without showing the resistance in the low temperature regime. Similar work also shows a difference in diamagnetic susceptibility between field cooled and zero field cooled samples, which is not consistent with a diamagnetic material, as would be required for the Meissner Effect. These results would appear to show a phase transition, perhaps like a metal – insulator transition, rather than a superconducting one. The presentation covering both sides of the debate has ben uploaded to our presentations page for people who are interested.

At the end, the audience voted against the motion and so we don’t support the view that graphene is a superconductor. We hope to run this idea again in a month or so and are looking for volunteers (!) to debate the next point. The final one before Christmas, myself and Jon Goss have been ‘volunteered’ to present and as we are the ones who normally ask all the questions to the students, this is definitely going to be brown trousers time! I suspect this will be followed by a social event, which hopefully will include a drink of something medicinal …

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