Nanotechnology Now

Our NanoNews Digest Sponsors



Heifer International

Wikipedia Affiliate Button


android tablet pc

Home > Press > A Grand Unified Theory of Exotic Superconductivity? Scientists introduce a general theoretical approach that describes all known forms of high-temperature superconductivity and their "intertwined" phases

Sťamus Davis
Sťamus Davis

Abstract:
Years of experiments on various types of high-temperature (high-Tc) superconductors-materials that offer hope for energy-saving applications such as zero-loss electrical power lines-have turned up an amazing array of complex behaviors among the electrons that in some instances pair up to carry current with no resistance, and in others stop the flow of current in its tracks. The variety of these exotic electronic phenomena is a key reason it has been so hard to identify unifying concepts to explain why high-Tc superconductivity occurs in these promising materials.

A Grand Unified Theory of Exotic Superconductivity? Scientists introduce a general theoretical approach that describes all known forms of high-temperature superconductivity and their "intertwined" phases

Upton, NY | Posted on October 17th, 2013

Now Sťamus Davis, a physicist who's conducted experiments on many of these materials at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory and Cornell University, and Dung-Hai Lee, a theorist at DOE's Lawrence Berkeley National Laboratory and the University of California, Berkeley, postulate a set of key principles for understanding the superconductivity and the variety of "intertwined" electronic phenomena that applies to all the families of high-Tc superconductors. They describe these general concepts in a paper published in the Proceedings of the National Academy of Sciences October 10, 2013.

"If we are right, this is kind of the 'light at the end of the tunnel' point," said Davis. "After decades of wondering which are the key things we need to understand high-Tc superconductivity and which are the peripheral things, we think we have identified what the essential elements are."

Said Lee, "The next step is to be able to predict which other materials will have these essential elements that will drive high Tc superconductivity-and that ability is still under development."

The role of magnetism

In all known types of high-Tc superconductors-copper-based (cuprate), iron-based, and so-called heavy fermion compounds-superconductivity emerges from the "extinction" of antiferromagnetism, the ordered arrangement of electrons on adjacent atoms having anti-aligned spin directions. Electrons arrayed like tiny magnets in this alternating spin pattern are at their lowest energy state, but this antiferromagnetic order is not beneficial to superconductivity.

However if the interactions between electrons that cause antiferromagnetic order can be maintained while the actual order itself is prevented, then superconductivity can appear. "In this situation, whenever one electron approaches another electron, it tries to anti-align its magnetic state," Davis said. Even if the electrons never achieve antiferromagnetic order, these antiferromagnetic interactions exert the dominant influence on the behavior of the material. "This antiferromagnetic influence is universal across all these types of materials," Davis said.

Many scientists have proposed that these antiferromagnetic interactions play a role in the ability of electrons to eventually pair up with anti-aligned spins-a condition necessary for them to carry current with no resistance. The complicating factor has been the existence of many different types of "intertwined" electronic phases that also emerge in the different types of high-Tc superconductors-sometimes appearing to compete with superconductivity and sometimes coexisting with it.

Intertwined phases

In the cuprates, for example, regions of antiferromagnetic alignment can alternate with "holes" (vacancies formerly occupied by electrons), giving these materials a "striped" pattern of charge density waves [http://www.bnl.gov/newsroom/news.php?a=1187]. In some instances this striped phase can be disrupted by another phase that results in distortions of the stripes [http://www.bnl.gov/newsroom/news.php?a=11307]. In iron-based superconductors, Davis' experiments revealed a nematic liquid-crystal-like phase [http://www.bnl.gov/newsroom/news.php?a=11061]. And in the heavy fermion superconductors, other exotic electronic states occur [http://www.bnl.gov/newsroom/news.php?a=11559].

"When so many intertwined phases were discovered in the cuprates, I was strongly discouraged because I thought, 'How are we going to understand all these phases?'" said Lee. But after the discovery of the iron-based superconductors about five years ago, and their similarities with the cuprates, Lee began to believe there must be some common factor. "Sťamus was thinking along a similar line experimentally," he said.

In the current paper, Davis and Lee propose and demonstrate within a simple model that antiferromagnetic electron interactions can drive both superconductivity and the various intertwined phases across different families of high-Tc superconductors. These intertwined phases and the emergence of superconductivity, they say, can be explained by how the antiferromagnetic influence interacts with another variable in their theoretical description, namely the "Fermi surface topology."

"The Fermi surface is a property of all metals and provides a 'fingerprint' of the specific arrangements of electrons that are free to move that is characteristic of each compound," Davis said. "It is controlled by how many electrons are in the crystal, and by the symmetry of the crystal, among other things, so it is quite different in different materials."

The theory developed by Lee incorporates the overarching antiferromagnetic electron interactions and the known differences in Fermi surface from material to material. Using calculations to "dial up" the strength of the magnetic interactions or vary the Fermi surface characteristics, the theory can predict the types of electronic phases that should emerge up to and including the superconductivity for all those different conditions.

"The basic assumption of our theory is that when we rip away all the complicated intertwined phases, underneath there is an ordinary metal," said Lee. "It is the antiferromagnetic interactions in this metal that make the electrons want to form the various states. The complex behavior originates from the system fluctuating from one state to another, e.g., from superconductor to charge density waves to nematic order. It is the antiferromagnetic interaction acting on the underlying simple metal that causes all the complexity."

"So far this theory has correctly produced all the electronic phases that we have observed in each type of strongly correlated superconductor," Davis said.

The next step is to search through new materials and use the theory to identify which should operate in similar ways-and then put them to the test to see if they follow the predictions.

"It is one thing to say, 'If we have the key ingredients, then a material is likely to exhibit high Tc superconductivity.' It is quite another thing to know which materials will have these key characteristics,'" Lee said.

If the search pays off, it could lead to the identification or development of superconductors that can be used even more effectively than those that are known today-potentially transforming our energy landscape.

This research was funded by the DOE Office of Science, in part through the Center for Emergent Superconductivity, a DOE-funded Energy Frontier Research Center at Brookhaven National Laboratory.

DOE's Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov

####

About Brookhaven National Laboratory
One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. Brookhaven is operated and managed for DOE's Office of Science by Brookhaven Science Associates, a limited-liability company founded by the Research Foundation for the State University of New York on behalf of Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit applied science and technology organization.

For more information, please click here

Contacts:
Karen McNulty Walsh
(631) 344-8350

or
Peter Genzer
(631) 344-3174

Copyright © Brookhaven National Laboratory

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

Scientific paper: "Concepts relating magnetic interactions, intertwined electronic orders, and strongly correlated superconductivity"

Related News Press

News and information

Atom-thick CCD could capture images: Rice University scientists develop two-dimensional, light-sensitive material December 20th, 2014

Oregon researchers glimpse pathway of sunlight to electricity: Collaboration with Lund University uses modified UO spectroscopy equipment to study 'maze' of connections in photoactive quantum dots December 19th, 2014

Instant-start computers possible with new breakthrough December 19th, 2014

Aculon Hires New Business Development Director December 19th, 2014

Physics

SUNY Poly NanoCollege Faculty Member Selected as American Physical Society Fellow: SUNY Poly Associate Professor of Nanoscience Dr. Vincent LaBella Recognized for Significant Technological Innovations that Enable Interactive Learning December 17th, 2014

Fraud-proof credit card possible because of quantum physics December 16th, 2014

Unusual Electronic State Found in New Class of Unconventional Superconductors: Finding gives scientists a new group of materials to explore to unlock secrets of some materials' ability to carry current with no energy loss December 8th, 2014

Laboratories

Switching to spintronics: Berkeley Lab reports on electric field switching of ferromagnetism at room temp December 17th, 2014

ORNL microscopy pencils patterns in polymers at the nanoscale December 17th, 2014

Student Nanotechnology Laboratories Network Set Up in Iran December 15th, 2014

Unusual Electronic State Found in New Class of Unconventional Superconductors: Finding gives scientists a new group of materials to explore to unlock secrets of some materials' ability to carry current with no energy loss December 8th, 2014

Superconductivity

Nanoscale resistors for quantum devices: The electrical characteristics of new thin-film chromium oxide resistors that can be tuned by controlling the oxygen content detailed in the 'Journal of Applied Physics' December 9th, 2014

Unusual Electronic State Found in New Class of Unconventional Superconductors: Finding gives scientists a new group of materials to explore to unlock secrets of some materials' ability to carry current with no energy loss December 8th, 2014

Govt.-Legislation/Regulation/Funding/Policy

Atom-thick CCD could capture images: Rice University scientists develop two-dimensional, light-sensitive material December 20th, 2014

Oregon researchers glimpse pathway of sunlight to electricity: Collaboration with Lund University uses modified UO spectroscopy equipment to study 'maze' of connections in photoactive quantum dots December 19th, 2014

Switching to spintronics: Berkeley Lab reports on electric field switching of ferromagnetism at room temp December 17th, 2014

ORNL microscopy pencils patterns in polymers at the nanoscale December 17th, 2014

Discoveries

Atom-thick CCD could capture images: Rice University scientists develop two-dimensional, light-sensitive material December 20th, 2014

Oregon researchers glimpse pathway of sunlight to electricity: Collaboration with Lund University uses modified UO spectroscopy equipment to study 'maze' of connections in photoactive quantum dots December 19th, 2014

Instant-start computers possible with new breakthrough December 19th, 2014

Iranian Scientists Use Nanotechnology to Increase Power, Energy of Supercapacitors December 18th, 2014

Announcements

Atom-thick CCD could capture images: Rice University scientists develop two-dimensional, light-sensitive material December 20th, 2014

Oregon researchers glimpse pathway of sunlight to electricity: Collaboration with Lund University uses modified UO spectroscopy equipment to study 'maze' of connections in photoactive quantum dots December 19th, 2014

Instant-start computers possible with new breakthrough December 19th, 2014

Aculon Hires New Business Development Director December 19th, 2014

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

Atom-thick CCD could capture images: Rice University scientists develop two-dimensional, light-sensitive material December 20th, 2014

Oregon researchers glimpse pathway of sunlight to electricity: Collaboration with Lund University uses modified UO spectroscopy equipment to study 'maze' of connections in photoactive quantum dots December 19th, 2014

Instant-start computers possible with new breakthrough December 19th, 2014

Iranian Scientists Use Nanotechnology to Increase Power, Energy of Supercapacitors December 18th, 2014

Research partnerships

Oregon researchers glimpse pathway of sunlight to electricity: Collaboration with Lund University uses modified UO spectroscopy equipment to study 'maze' of connections in photoactive quantum dots December 19th, 2014

Unraveling the light of fireflies December 17th, 2014

Scientists trace nanoparticles from plants to caterpillars: Rice University study examines how nanoparticles behave in food chain December 16th, 2014

FEI and Oregon Health & Science University Install a Complete Correlative Microscopy Workflow in Newly Built Collaborative Science Facility December 16th, 2014

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







© Copyright 1999-2014 7th Wave, Inc. All Rights Reserved PRIVACY POLICY :: CONTACT US :: STATS :: SITE MAP :: ADVERTISE