by Staff Writers
Toronto, Canada (SPX) Mar 23, 2015
CIFAR fellows were among physicists who observed the shape of a strange phenomenon that interferes with high-temperature superconductivity called charge ordering, discovering that it is stripy, not checkered, and settling a long-standing debate in the field.
Charge ordering creates instability in some metals at temperatures warmer than about -100 degrees Celsius, causing some electrons to reorganize into new periodical static patterns competing with superconductivity. But scientists wonder if it may also play an essential role in propelling electrons into the tight pairs that allow them to travel without resistance.
In order to understand what charge ordering does, and whether it's a hindrance, a help, or a bit of both, scientists must first understand what it is - starting with its shape.
Riccardo Comin, lead author on a new paper in Science, set out to determine whether the pattern of charge ordering was a checkerboard or a series of stripes by x-raying very cold yttrium barium copper oxide. His collaborators at the Quantum Matter Institute of the University of British Columbia included CIFAR Global Scholar Eduardo da Silva Neto and senior fellows of the Quantum Materials program Ruixing Liang, Walter Hardy, Doug Bonn, George Sawatzky, and Andrea Damascelli - who is Comin's PhD supervisor and team leader of this study.
They found the pattern is striped, meaning the electrons self-organize along one direction (1D), rather than in two directions (2D) as they would in a checkerboard pattern. However, when the temperature cools down far enough, charge ordering dies off and superconductivity takes over, allowing electrons to travel freely with no resistance, no longer constrained to one dimension.
The result is exciting because physics is much more interesting in low dimension, says Damascelli. And in the cuprates these 1D patterns are realized within the 2D Cu-O planes, which already con-strain the motion of electron to less than 3D, even before charge ordering sets in.
"Superconductivity in conventional 3D metals is limited to a Tc of few degrees Kelvin," he says, citing examples such as aluminum and niobium. "High temperature superconductors are quasi 2D metals, and now with a tendency toward 1D electronic ordering."
Furthermore, the researchers found that charge ordering competes with superconductivity much more strongly along one direction than the other. The results are an important step in knowing what drives superconductivity and what my hinder it.
"Is charge ordering just an anomaly, or is it there in all these systems because there is an underlying interaction which isn't completely removed from superconductivity?" Comin asks. "The two phenomena are competing but in a sense they're also interconnected."
Damascelli says the material in this study, yttrium barium copper oxide, is the superstar of copper-oxides because of its exquisite purity and high transition temperature. It's also a Canadian success story - CIFAR fellows Liang-Bonn-Hardy are leading growers and suppliers of the crystal for re-search the world over. "That's why the Canadian groups and in particular the CIFAR program has had such an impact, because we had access to the best materials," Damascelli says.
Canadian Institute for Advanced Research
Powering The World in the 21st Century at Energy-Daily.com
|The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.|