The discovery of dual metal-insulator behaviour in a single material has the potential to overturn decades of conventional wisdom regarding the fundamental dichotomy between metals and insulators
- Suchitra Sebastian
A new study has discovered mysterious behaviour of a material that acts like an insulator in certain measurements, but simultaneously acts like a conductor in others. In an insulator, electrons are largely stuck in one place, while in a conductor, the electrons flow freely. The results, just published in the journal Science, challenge current understanding of how materials behave.
Conductors, such as metals, conduct electricity, while insulators, such as rubber or glass, prevent or block the flow of electricity. But by tracing the path that electrons follow as they move through a material, researchers led by the University of Cambridge found that it is possible for a single material to display dual metal-insulator properties at once – although at the very lowest temperatures, it completely disobeys the rules that govern conventional metals. While it’s not known exactly what’s causing this mysterious behaviour, one possibility is the existence of a potential third phase which is neither insulator nor conductor.
The duelling metal-insulator properties were observed throughout the interior of the material, called samarium hexaboride (SmB6). There are other recently-discovered materials which behave both as a conductor and an insulator, but they are structured like a sandwich, so the surface behaves differently from the bulk. But the new study found that in SmB6, the bulk itself can be both conductor and insulator simultaneously.
“The discovery of dual metal-insulator behaviour in a single material has the potential to overturn decades of conventional wisdom regarding the fundamental dichotomy between metals and insulators,” said Dr Suchitra Sebastian of the University’s Cavendish Laboratory, who led the research.
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Image: PhD student Maria Kiourlappou holding a piece of SmB6
Credit: Suchitra Sebastian
Reproduced courtesy of the University of Cambridge
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