Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Complex order parameter in ruthenate superconductors confirmed

29.11.2006
Since it was discovered to be superconducting over a decade ago, the pairing symmetry of strontium ruthenium oxide has been widely explored and debated. Now, a team of researchers led by Dale Van Harlingen at the University of Illinois at Urbana-Champaign say the debate is over.

“We have pretty unambiguous evidence for ‘p-wave’ symmetry with a complex order parameter that breaks time-reversal symmetry in this ruthenate superconductor,” said Van Harlingen, a Willett Professor and head of the department of physics at Illinois.

Until now, this complex odd symmetry state had been predicted by theoreticians, but never fully confirmed. Van Harlingen and colleagues report their latest findings in the Nov. 24 issue of the journal Science.

The order parameter of a superconductor characterizes the nature of the pairing interaction that forms Cooper pairs. It controls many of the superconductor’s properties, and provides a crucial clue to the microscopic mechanism responsible for the superconductivity.

Conventional superconductors that form Cooper pairs through phonon interactions have an “s-wave” symmetry with an isotropic order parameter. Unconventional superconductors, however, have anisotropy in either or both the phase and magnitude of the order parameter.

Ten years ago, Van Harlingen’s group pioneered the Josephson interferometer technique that showed the high-temperature superconducting cuprates had “d-wave” symmetry. They are now applying the technique to a wide range of superconducting materials suspected of having unconventional symmetry.

“Our technique can directly measure phase differences in the superconducting order parameter,” said Van Harlingen, who is also a researcher at the university’s Micro and Nanotechnology Laboratory, and a professor in the university’s Center for Advanced Study, one of the highest forms of campus recognition. “This allows us to make an unambiguous determination of the pairing symmetry in unconventional superconductors,” he said.

To use their interferometer technique, the researchers begin by constructing a corner Josephson junction that straddles different faces of a single crystal of the ruthenate superconductor. They then measure the magnetic field modulation of the supercurrent that reveals the phase shift between different tunneling directions.

If all areas of a Josephson junction have the same order parameter phase, the critical current (measured as a function of applied magnetic field) will create a Fraunhofer diffraction pattern, analogous to a single-slit optical diffraction pattern. However, phase differences in the order parameter on adjacent crystal faces of a corner junction, or the presence of chiral domains (characterized by the direction of phase winding) along a single junction face, will result in modulated diffraction patterns.

“We observed highly modulated diffraction patterns across single edge junctions, which implies the existence of chiral domains,” Van Harlingen said. Abrupt changes seen in the diffraction patterns as a function of magnetic field or time indicate these domains are dynamical, changing their size or orientation.

“The presence of these domains and the distinctly different diffraction patterns observed on orthogonal faces of the same single crystal confirms the ‘p-wave’ triplet spin pairing state and the complex nature of the superconducting order parameter in the ruthenate superconductors,” Van Harlingen said.

James E. Kloeppel | EurekAlert!
Further information:
http://www.uiuc.edu

More articles from Physics and Astronomy:

nachricht SF State astronomer searches for signs of life on Wolf 1061 exoplanet
20.01.2017 | San Francisco State University

nachricht Molecule flash mob
19.01.2017 | Technische Universität Wien

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Helmholtz International Fellow Award for Sarah Amalia Teichmann

20.01.2017 | Awards Funding

An innovative high-performance material: biofibers made from green lacewing silk

20.01.2017 | Materials Sciences

Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery

20.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>