Team uncovers unconventional superconductivity

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By Roger Snodgrass

An international team of researchers working at Los Alamos published a paper in the scientific journal Nature proposing an “unconventional” approach to superconductivity.


The work has emerged from a series of discoveries over the last several years, involving the interplay of traditional cold temperatures and magnetism with a newly identified boundary area governed by quantum physics.


Electricity, for all the good it does as a relatively inexpensive form of easily distributed energy is still less than fully efficient.


Some 20 percent of electrical energy goes to waste as heat from transmission wires.


Superconductivity, a special state of matter in which electrons can move without resistance, promises a sizeable energy dividend, if it can be accomplished at a warmer temperature.


Currently, even so-called “high temperature” superconductivity is far from warm. Industrially engineered superconductivity is now practical for some highly specialized purposes like magnetic resonance imaging and particle accelerators, but not for ordinary use.


Progress along this path, known as conventional superconductivity, has been meager for some time now, to the point that some researchers, including the team at Los Alamos National Laboratory, have focused on an alternative involving magnetic fluctuations.


“Conventional approaches are not going to get us there. We need a new mechanism,” said Joe Thompson a LANL scientist of the team that conducted the new experiments. “We’re looking for another form of excitation.”


The experimenters cooled a compound of Cerium, Rhodium and Indium to .08 Kelvin, a fraction above absolute zero, adding pressure and a magnetic field to perturb the alignment of electrons with the material.


A laboratory announcement explained that conventional theories of superconductivity describe a mechanism by which electrons pair up under the influence of atomic vibrations known as phonons, which “provide the ‘glue’ that makes the superconductor possible.


But other mechanisms for attractiveness between the electrons have also been known for decades, including phenomena related to the spin and charge of the electrons.


“We introduced very high quantum fluctuations in the material,” Park said. “In other words, we made the electrons like a traffic jam, where it would be very difficult for them to move.”


One of the peculiar things about the new kind of superconductivity that resulted is that it can’t be observed.


“The presence of superconductivity prevents us from seeing inside,” said Tuson Park of LANL, the lead author of the current paper.


He said the experiment offered a new approach to some lingering mysteries.


Thompson added that the findings would direct some “well defined experiments we will do over the next six months.”


“This previously unanticipated source of pairing glue opens possibilities for understanding and discovering new unconventional forms of superconductivity,” write the authors of the paper in their introductory abstract.


The ultimate hope is that the new research will lead to an alternative pathway to room-temperature superconductivity.