Featured Research

from universities, journals, and other organizations

New State Of Matter Found In High-Temperature Superconductors

Date:
September 9, 1997
Source:
University Of Illinois At Urbana-Champaign
Summary:
Scientists at the University of Illinois -- working with scientists at Northwestern University -- have discovered the first example of a solid superconductor displaying broken time-reversal symmetry.

CHAMPAIGN, Ill. -- Recent experiments on yttrium-barium-copper-oxide (YBCO) superconductors have generated a clearer understanding of the peculiar behavior of this unconventional material. Most significant among the findings, by studying a characteristic called the zero-bias conductance peak, scientists at the University of Illinois -- working with scientists at Northwestern University -- have discovered the first example of a solid superconductor displaying broken time-reversal symmetry.

Related Articles


"The really hot news in the field of high-temperature superconductors is that the zero-bias conductance peak splits at low temperatures in the absence of an externally applied magnetic field," said Laura Greene, a U. of I. professor of physics who directed the research effort. "Not only does our experiment again prove that the dominant symmetry in YBCO superconductors is d-wave, it also shows that two different pairing mechanisms -- or order parameters -- can coexist in the same material, creating spontaneous currents that are a signature of broken time-reversal symmetry."

The surprising result offers proof of a new state of matter that has eluded researchers for years, Greene said. "This is the first case of a solid superconductor breaking both gauge symmetry and time-reversal symmetry. The only other material proven to break both symmetries is the unconventional superfluid helium-3, the discovery of which was awarded the 1996 Nobel Prize in physics."

To perform the experiment, Greene and her colleagues grew thin films of YBCO by off-axis magnetron sputter deposition. The researchers then used planar tunneling spectroscopy to measure the tunneling conductance across different junctions as a function of crystallographic orientation, temperature and externally applied magnetic field.

"Our team of experimentalists worked closely with Jim Sauls, a theorist at Northwestern," Greene said. "In fact, our two papers appeared together in the July 14 issue of Physical Review Letters. What we found was exactly what Sauls had predicted."

According to the experimental results, at 90 degrees Kelvin (the critical temperature for YBCO) the superconductor has d-wave symmetry, Greene said. "When cooled to about 7 degrees Kelvin, however, a second superconducting channel opens up which has s-wave symmetry. Because the two symmetries coexist, the differences between their phases spontaneously generate a current. The current creates a magnetic field, and that is what splits the zero-bias conductance peak."

The spontaneously generated current is also what breaks the time-reversal symmetry, Greene said. "Because the current is flowing in a certain direction, you can tell whether it's going forward or backward with respect to time."

The research team also comprised Mark Covington, Marco Aprili and Elvira Paraoanu at the U. of I., and Chad Mirkin, Feng Xu and Jun Zhu at Northwestern. The research was supported by the National Science Foundation through the Science and Technology Center for Superconductivity.


Story Source:

The above story is based on materials provided by University Of Illinois At Urbana-Champaign. Note: Materials may be edited for content and length.


Cite This Page:

University Of Illinois At Urbana-Champaign. "New State Of Matter Found In High-Temperature Superconductors." ScienceDaily. ScienceDaily, 9 September 1997. <www.sciencedaily.com/releases/1997/09/970909054942.htm>.
University Of Illinois At Urbana-Champaign. (1997, September 9). New State Of Matter Found In High-Temperature Superconductors. ScienceDaily. Retrieved October 25, 2014 from www.sciencedaily.com/releases/1997/09/970909054942.htm
University Of Illinois At Urbana-Champaign. "New State Of Matter Found In High-Temperature Superconductors." ScienceDaily. www.sciencedaily.com/releases/1997/09/970909054942.htm (accessed October 25, 2014).

Share This



More Matter & Energy News

Saturday, October 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

IKEA Desk Converts From Standing to Sitting With One Button

IKEA Desk Converts From Standing to Sitting With One Button

Buzz60 (Oct. 24, 2014) IKEA is out with a new convertible desk that can convert from a sitting desk to a standing one with just the push of a button. Jen Markham explains. Video provided by Buzz60
Powered by NewsLook.com
Ebola Protective Suits Being Made in China

Ebola Protective Suits Being Made in China

AFP (Oct. 24, 2014) A factory in China is busy making Ebola protective suits for healthcare workers and others fighting the spread of the virus. Duration: 00:38 Video provided by AFP
Powered by NewsLook.com
Real-Life Transformer Robot Walks, Then Folds Into a Car

Real-Life Transformer Robot Walks, Then Folds Into a Car

Buzz60 (Oct. 24, 2014) Brave Robotics and Asratec teamed with original Transformers toy company Tomy to create a functional 5-foot-tall humanoid robot that can march and fold itself into a 3-foot-long sports car. Jen Markham has the story. Video provided by Buzz60
Powered by NewsLook.com
Police Testing New Gunfire Tracking Technology

Police Testing New Gunfire Tracking Technology

AP (Oct. 24, 2014) A California-based startup has designed new law enforcement technology that aims to automatically alert dispatch when an officer's gun is unholstered and fired. Two law enforcement agencies are currently testing the technology. (Oct. 24) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins