A possible cause of the 'strange'
behavior of cuprates, special superconductor materials made of
copper and oxygen which could in future bring down waste in the
distribution of electricity, has been revealed.
The result, which shows promise in paving the way for more
sustainable technologies, has been published in Nature
Communications by researchers from the Politecnico in Milan, the
Chalmers University of Technology in Gothenborg and Rome's
Sapienza University.
Superconductors are materials in which electric current travels
without resistance below a certain temperature: this sets them
apart from normal metals in which resistance entails the
production of heat and therefore a waste of energy. Cuprates, in
particular, are superconductor materials which at a temperature
above critical (when they are in the 'normal' state and
therefore do not have zero resistance) behave in an
unconventional way, so much so that they are called 'strange'
metals.
The strangeness lies in the linear increase in resistivity with
temperature, something that does not happen in normal metals.
Thanks to X-ray diffusion experiments conducted at the European
Synchrotron ESRF and the Britisn synchrotron Diamond Light
Source, the researchers have discovered that what makes cuprates
'strange' are fluctuations in load density capable of
influencing electrical resistance. The systematic measurement of
how the energy of these fluctuations varies has enabled
researchers to identify the exact value of the density of the
load bearers where it is minimal: the quantum critical point.
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