Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > Material turns 'schizophrenic' on way to superconductivity - Strange state: Some electrons remain mobile while their neighbors are locked down

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

CREDIT: Jeff Fitlow/Rice University

Abstract:
Rice University physicists on the hunt for the origins of high-temperature superconductivity have published new findings this week about a material that becomes "schizophrenic" -- simultaneously exhibiting the characteristics of both a metallic conductor and an insulator.

Material turns 'schizophrenic' on way to superconductivity - Strange state: Some electrons remain mobile while their neighbors are locked down

Houston, TX | Posted on April 4th, 2013

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 "schizophrenic" 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 unified phase diagram for the alkaline iron selenides in which this schizophrenic 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 schizophrenic 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 schizophrenic 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.

The research was funded by the National Science Foundation and the Robert A. Welch Foundation.

####

About Rice University
Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation's top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 3,708 undergraduates and 2,374 graduate students, Rice's undergraduate student-to-faculty ratio is 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice has been ranked No. 1 for best quality of life multiple times by the Princeton Review and No. 2 for "best value" among private universities by Kiplinger's Personal Finance. To read "What they're saying about Rice," go to tinyurl.com/AboutRiceU.

Follow Rice News and Media Relations via Twitter @RiceUNews

For more information, please click here

Contacts:
David Ruth
713-348-6327


Jade Boyd
713-348-6778

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related Links

A copy of the PRL paper is available at:

Related News Press

News and information

Particles from outer space are wreaking low-grade havoc on personal electronics February 19th, 2017

Liquid metal nano printing set to revolutionize electronics: Creating integrated circuits just atoms thick February 18th, 2017

Engineers shrink microscope to dime-sized device February 17th, 2017

Francis Alexander Named Deputy Director of Brookhaven Lab's Computational Science Initiative February 16th, 2017

Superconductivity

Research reveals novel quantum state in strange insulating materials February 14th, 2017

Portable superconductivity systems for small motors: Cambridge University lab achieves a breakthrough for portable superconductivity systems that are applicable for small motors, health care and other uses February 8th, 2017

Metallic hydrogen, once theory, becomes reality: Harvard physicists succeed in creating 'the holy grail of high-pressure physics' January 28th, 2017

Graphene's sleeping superconductivity awakens: Since its discovery in 2004, scientists have believed that graphene may have the innate ability to superconduct. Now Cambridge researchers have found a way to activate that previously dormant potential January 24th, 2017

Govt.-Legislation/Regulation/Funding/Policy

Engineers shrink microscope to dime-sized device February 17th, 2017

Francis Alexander Named Deputy Director of Brookhaven Lab's Computational Science Initiative February 16th, 2017

Good vibrations help reveal molecular details: Rice University scientists combine disciplines to pinpoint small structures in unlabeled molecules February 15th, 2017

Research reveals novel quantum state in strange insulating materials February 14th, 2017

Discoveries

Particles from outer space are wreaking low-grade havoc on personal electronics February 19th, 2017

Liquid metal nano printing set to revolutionize electronics: Creating integrated circuits just atoms thick February 18th, 2017

Engineers shrink microscope to dime-sized device February 17th, 2017

Research opens door to smaller, cheaper, more agile communications tech February 16th, 2017

Materials/Metamaterials

Metamaterial: Mail armor inspires physicists: KIT researchers reverse hall coefficient -- medieval mail armor inspired development of metamaterial with novel properties February 15th, 2017

Research reveals novel quantum state in strange insulating materials February 14th, 2017

Graphene foam gets big and tough: Rice University's nanotube-reinforced material can be shaped, is highly conductive February 13th, 2017

Researchers optimize the assembly of micro-/meso-/macroporous carbon for Li-S batteries February 13th, 2017

Announcements

Particles from outer space are wreaking low-grade havoc on personal electronics February 19th, 2017

Liquid metal nano printing set to revolutionize electronics: Creating integrated circuits just atoms thick February 18th, 2017

Engineers shrink microscope to dime-sized device February 17th, 2017

Francis Alexander Named Deputy Director of Brookhaven Lab's Computational Science Initiative February 16th, 2017

Interviews/Book Reviews/Essays/Reports/Podcasts/Journals/White papers

Particles from outer space are wreaking low-grade havoc on personal electronics February 19th, 2017

Liquid metal nano printing set to revolutionize electronics: Creating integrated circuits just atoms thick February 18th, 2017

Engineers shrink microscope to dime-sized device February 17th, 2017

Research opens door to smaller, cheaper, more agile communications tech February 16th, 2017

Energy

In-cell molecular sieve from protein crystal February 14th, 2017

NREL research pinpoints promise of polycrystalline perovskites February 8th, 2017

Metallic hydrogen, once theory, becomes reality: Harvard physicists succeed in creating 'the holy grail of high-pressure physics' January 28th, 2017

New low-cost technique converts bulk alloys to oxide nanowires January 24th, 2017

Grants/Awards/Scholarships/Gifts/Contests/Honors/Records

Good vibrations help reveal molecular details: Rice University scientists combine disciplines to pinpoint small structures in unlabeled molecules February 15th, 2017

Material can turn sunlight, heat and movement into electricity -- all at once: Extracting energy from multiple sources could help power wearable technology February 9th, 2017

National Space Society Honors NASA's William H. Gerstenmaier With 2017 Space Pioneer Award January 31st, 2017

The Kepler-K2 Team Wins the National Space Society's 2017 Space Pioneer Award for Science and Engineering January 29th, 2017

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project