Free Newsletters - Space - Defense - Environment - Energy - Solar - Nuclear
..
. 24/7 Space News .




ENERGY TECH
Electron conflict leads to 'bad traffic' on way to superconductivity
by Staff Writers
Houston TX (SPX) Apr 09, 2013


These are Rice University physicists Qimiao Si (left) and Rong Yu. Credit: Jeff Fitlow/Rice University.

Rice University physicists on the hunt for the origins of high-temperature superconductivity have published new findings this week about a seemingly contradictory state in which a material simultaneously exhibits the conflicting characteristics of both a metallic conductor and an insulator.

In a theoretical analysis this week in Physical Review Letters (PRL), Rice physicists Qimiao Si and Rong Yu offer an explanation for a strange series of observations described earlier this year by researchers at the Stanford Linear Accelerator Center in Menlo Park, Calif. In those experiments, physicists used X-rays to probe the behavior of electrons in superconducting materials made of potassium, iron and selenium.

The material becomes superconducting at extremely cold temperatures, and the experiments revealed that at a slightly higher temperature, the material exhibited a seemingly contradictory electronic state in which some electrons in the iron atoms became frozen in place while electrons in neighboring orbitals continued to move.

"We have proposed a uni?ed phase diagram for the alkaline iron selenides in which this phase connects between the lower-temperature, superconducting phase at one extreme and a higher-temperature insulating phase at the other," said Si, Rice's Harry C. and Olga K. Wiess Professor of Physics and Astronomy.

Flowing electrons power all the world's energy grids, and a significant amount of power in those grids is lost to electrical resistance -- a kind of electronic friction that occurs when electrons move through metallic wires. Superconducting materials, which were discovered more than a century ago, conduct electricity without any loss of power, but they only operate at extremely cold temperatures.

Since the 1980s, scientists have discovered a number of new materials that become superconducting at temperatures that, while still cold, are above or close to the temperature of liquid nitrogen -- an important threshold for engineering applications.

The hope is that these "high-temperature" superconductors may one day be used to revolutionize power transmission and other technologies, but physicists have yet to develop a clear-cut understanding of how high-temperature superconductors work.

In classical superconductors, frictionless conduction is achieved when electrons pair up in a way that allows them to flow effortlessly, without the bumping and jostling that normally leads to electrical resistance. Electron pairing is uncommon because the rules of quantum mechanics typically make electrons loners.

Under normal circumstances, electrons repel one another, and the mechanism that causes them to pair up in classical superconductors doesn't account for their behavior in high-temperature superconductors.

Iron-based high-temperature superconductors were discovered in 2008. Si and collaborators, including UCLA physicist Elihu Abrahams, were among the first to propose a way in which superconductivity might arise in the iron-based materials due to a phenomenon known as "correlated electron" behavior.

In correlated-electron systems, the behavior of electrons in a material can only be understood by viewing the electrons as a collective system rather than many individual objects.

Si and Yu's new paper focuses on experiments with an alkaline iron selenide, one family of materials that is included in the larger class of iron-based superconductors. Prior experiments had found that alkaline iron selenides exhibited odd electronic behaviors at temperatures above the critical temperature in which they transition to the superconducting state.

In the PRL paper, Si and Yu describe a new electronic state, or phase, marked by electronic traffic congestion. They show that electrons in different quantum states, or orbitals, react differently to the bad traffic situation. In particular, the new phase is marked by electrons in selected orbitals becoming locked in a place -- a phenomenon known as a Mott insulating state.

"In a theoretical model containing several orbitals, we identified an 'orbital-selective Mott phase,'" said Yu, a postdoctoral research associate at Rice. "In this phase, electrons in some orbitals behave like an insulator, while those in the other orbitals act as a metal."

Si and Yu said they saw the first hints of the new phase in a 2011 model they designed to study a different family of iron-based superconductors. In that model, the orbital-selective Mott phase ultimately proved to be unstable, so they were somewhat surprised when the phase appeared and proved stable in the model for the alkaline iron selenides.

"This is the first time anybody has identified an orbital-selective Mott phase in any model for the iron-based superconductors," Yu said.

Si said characterizing the orbital-selective Mott phase in the alkaline iron selenides provides more clues about the fundamental origins of superconductivity.

"Ultimately, our goal is to understand superconductivity and the conditions to optimize superconductivity," Si said.

The premise is that this kind of bad traffic situation -- the contradictory phase where electrons are in conflict as to whether they should freeze or move -- is good for superconductivity.

"Our results provide evidence that electron correlations play a vital role in the superconductivity of the iron-based superconductors," he said.

A copy of the PRL paper is available here.

.


Related Links
Rice University
Powering The World in the 21st Century at Energy-Daily.com






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





ENERGY TECH
Light tsunami in a superconductor
Munich, Germany (SPX) Apr 05, 2013
In their latest experiment, Prof. Andrea Cavalleri from the Max Planck Institute for the Structure and Dynamics of Matter at the Hamburg-based Center for Free-Electron Laser Science (CFEL) and Dr. Michael Gensch from the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) investigated together with other colleagues from the HZDR, the United Kingdom, and Japan if and how superconductivity can be systemat ... read more


ENERGY TECH
Russia rekindles Moon exploration program, intends setting up first human outposts there

Pre-existing mineralogy may survive lunar impacts

Lunar cycle determines hunting behaviour of nocturnal gulls

Ultraviolet spectrograph observes mercury and hydrogen in GRAIL impact plumes

ENERGY TECH
Registration Opens for NASA Night Rover Energy Challenge

Final MAVEN Instrument Integrated to Spacecraft

Used Parachute on Mars Flaps in the Wind

BusinessCom Networks Connects Mars 2013

ENERGY TECH
NASA Celebrates Four Decades of Plucky Pioneer 11

Do Intellectual Property Rights on Existing Technologies Hinder Subsequent Innovation

Boeing Completes Preliminary Design Review for Connection Between CST-100 Spacecraft and Rocket

NASA Invests in Small Business Innovative Research and Technology Proposals to Enable Future Missions

ENERGY TECH
Shenzhou's Shadow Crew

Shenzhou 10 sent to launch site

China's Next Women Astronauts

Shenzhou 10 - Next Stop: Jiuquan

ENERGY TECH
Spooky action at a distance aboard the ISS

First data released from the Alpha Magnetic Spectrometer

Alpha Magnetic Spectrometer Team Publishes First Findings

New crew takes express ride to space station

ENERGY TECH
Future Looks Bright for Private US Space Ventures

Europe's next ATV resupply spacecraft enters final preparatio?ns for its Ariane 5 launch

ILS Proton Launches Satmex 8 Satellite for Satmex

When quality counts: Arianespace reaffirms its North American market presence

ENERGY TECH
The Great Exoplanet Debate

NASA Selects Explorer Investigations for Formulation

The Great Exoplanet Debate Part Four

Astronomers Anticipate 100 Billion Earth-Like Planets

ENERGY TECH
What's between a slip and a slide?

Light may recast copper as chemical industry 'holy grail'

New camera system creates high-resolution 3-D images from up to a kilometer away

Theory and practice key to optimized broadband, low-loss optical metamaterials




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal 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