Researchers in Germany have presented further evidence for room temperature superconductivity in regions of graphite samples. Other experts, however, remain cautious about the interpretation of the measurements. Meanwhile, a scientist in Japan has made the astonishing claim that he packed a ring-shaped container with octane-soaked graphite flakes and induced a current within the ring which persisted without decay for 50 days. But superconductivity specialists say that the paper is thin on experimental detail and the necessary checks haven’t been done.
Pablo Esquinazi at the University of Leipzig claimed last year that his team seemed to have caught glimpses of room temperature superconductivity in samples of graphite powder that had been mixed with water and dried.1 At the time other specialists in the field such as Ted Forgan of the University of Birmingham in the UK and Archie Campbell of Cambridge University in the UK counselled caution in the interpretation of the results.
Now, Esquinazi and colleagues have provided more evidence of what they say is the presence of superconducting regions at interfaces within graphite samples. In one series of experiments the team shows that when electrical contacts are made at the edges of interfaces in samples of highly oriented pyrolytic graphite (HOPG), at low enough temperatures and currents, electrical resistance disappears.2 ‘The whole behaviour is compatible with the existence of granular superconductivity located at the interfaces of those graphite samples,’ Esquinazi says. A second series of experiments measuring the magnetisation of HOPG samples with well-defined interfaces produces a hysteresis loop similar to that obtained with the water-treated samples.3 Bulk samples without interfaces did not show this behaviour. ‘Therefore the results in the earlier work do not appear to be an artefact of background subtraction,’ Esquinazi contends.To read more, click here.