This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Superconductivity has many important practical applications, including creating powerful magnets used in high-resolution medical scans, transporting electricity efficiently and building ultrasensitive measuring devices. Until now, understanding exactly what lay behind this unique phenomenon at high temperatures has eluded scientists over many decades.
But research, led by physicists at the University of Bristol and published this week in the journal Nature Physics, has identified the mechanism which explains how electrons in these copper-oxide high-temperature superconductors combine to transmit power with no loss of energy—the 'superconductive' state of infinite electrical conduction. Study co-lead author Nigel Hussey, professor of physics at the University of Bristol, said, "Superconductivity is a remarkable, almost magical, phenomenon which has long fascinated famous physicists and resulted in various breakthroughs recognized with Nobel Prizes over the decades. "The processes which facilitate higher-temperature superconductivity, however, have remained a source of mystery and fascination.
Through measurements carried out at the European Magnetic Field Laboratory in the Netherlands and subsequent careful analysis, we have found the smoking gun which solves part of the equation and explains what causes this perplexing state." In conventional, lower-temperature superconductors, the mechanism through which electrons undergo superconductivity involves the vibrations of the ions that make up the crystalline lattice of the material. For many years scientists have been searching for a new mechanism for high-temperature superconductivity, likely involving entities that vibrate at higher frequencies than the ions themselves. Electrons were the prime candidate as they possess both a spin—like a spinning top, producing a tiny magnetic field—and a charge producing a current that can fluctuate in space and time.
Although spin and charge fluctuations have been mapped out in detail in these copper-oxide materials, in large part thanks to the endeavors of professor Stephen Hayden and his group at Bristol, evidence linking the strength of interaction between the conduction electrons and these fluctuations together with Tc—the critical temperature below which the material goes superconducting—has been missing. As with conventional superconductors, however, this information is encoded in the resistance of the material, and unlocking this information from the resistance itself was believed to hold the key to identifying the relevant interaction. So the team of international scientists from Bristol, the Netherlands, China and the U.S. created a special thin-film cuprate sample, in this case, lanthanum cerium copper oxide, and deposited it layer-by-atomic-layer onto a substrate to create a smooth gradient of Tc—from its maximum value to zero—along its entire length.
Using lithography, the researchers then patterned a series of electrical contacts along the film to enable the resistance to be measured as a function of finely spaced values of Tc while keeping the level of disorder across the film the same. A series of experiments were performed at the high magnetic field facility to extract the change in resistance as a function of temperature, magnetic field strength and Tc. Study lead experimentalist Dr.
Caitlin Duffy, a postdoctoral researcher at the French National Center for Scientific Research and former Ph.D. student of Hussey, explained, "Employing some analytical tricks on the data obtained in high magnetic fields, we were then able to identify the dominant source of resistance in this material as scattering off the fluctuating spins. "The correlation between the strength of this interaction and Tc then confirmed that the origin for superconductivity in this material is indeed the interaction between the conduction electrons and spin fluctuations." Discover the latest in science, tech, and space with over 100,000 subscribers who rely on Phys.org for daily insights. d research that matter—daily or weekly. While this in itself constitutes a major breakthrough, the researchers have only solved half of the superconductivity riddle, as there are two ways of inducing superconductivity in the parent copper-oxide.
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