Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New theory explains enhanced superconductivity in nanowires

20.10.2006
Superconducting wires are used in magnetic resonance imaging machines, high-speed magnetic-levitation trains, and in sensitive devices that detect variations in the magnetic field of a brain. Eventually, ultra-narrow superconducting wires might be used in power lines designed to carry electrical energy long distances with little loss.

Now, researchers at the University of Illinois at Urbana-Champaign not only have discovered an unusual phenomenon in which ultra-narrow wires show enhanced superconductivity when exposed to strong magnetic fields, they also have developed a theory to explain it.

Magnetic fields are generally observed to suppress a material's ability to exhibit superconductivity – the ability of materials to carry electrical current without any resistance at low enough temperatures. Deviations from this convention have been observed, but there is no commonly accepted explanation for these exceptions, although several ideas have been proposed.

As reported in the Sept. 29 issue of Physical Review Letters, U. of I. physics professor Alexey Bezryadin (pronounced BEZ-ree-ah-dun) and his research group have studied the effect of applying a magnetic field to ultra-narrow superconducting wires only a few hundred atoms across, and have used a microscopic theory proposed by physics professor Paul Goldbart and his team to explain the results.

"My group discovered that magnetic fields can enhance the critical current in superconducting wires with very small diameters," Bezryadin said. "We spoke with many colleagues and reached the consensus that this phenomenon is indeed curious."

Magnetic fields have long been known to suppress superconductivity by raising the kinetic energy of the electrons and by influencing the electron spins. Magnetic atoms, if present in the wires, also inhibit superconductivity.

Nevertheless, as reported in the Sept. 15 issue of Europhysics Letters, Goldbart, postdoctoral researcher Tzu-Chieh Wei and graduate student David Pekker proposed that the enhancement observed by Bezyradin's group was due to magnetic moments in the wires.

"Even though the two effects – magnetic fields and magnetic moments – work separately to diminish superconductivity, together one effect weakens the other, leading to an enhancement of the superconducting properties, at least until very large fields are applied," Goldbart said.

As for the origin of these magnetic moments, the collaborating groups proposed that exposure of the wires to oxygen in the atmosphere causes magnetic moments to form on the wire surfaces. On their own, the moments weaken the superconductivity, but the magnetic field inhibits their ability to do this. This effect shows up in ultra-narrow wires because so many of their atoms lie near the surface, where the magnetic moments form.

With postdoctoral research associate Andrey Rogachev (now a physics professor at the University of Utah) and graduate student Anthony Bollinger, Bezryadin deposited either niobium or an alloy of molybdenum and germanium onto carbon nanotubes to fabricate wires that were less than 10 nanometers wide. The superconductivity of these wires under a range of applied magnetic fields was examined, and the experimental results were compared with the proposed theory, revealing an excellent correlation between the two.

"The results of this work may provide a key to explaining our previous findings that nanowires undergo an abrupt transition from superconductor to insulator as they get smaller," said Bezryadin, referring to work published in the Sept. 27 issue of Europhysics Letters.

Kristen Aramthanapon | EurekAlert!
Further information:
http://www.uiuc.edu

More articles from Physics and Astronomy:

nachricht One-way roads for spin currents
23.05.2018 | Singapore University of Technology and Design

nachricht Tunable diamond string may hold key to quantum memory
23.05.2018 | Harvard John A. Paulson School of Engineering and Applied Sciences

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: LZH showcases laser material processing of tomorrow at the LASYS 2018

At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.

At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...

Im Focus: Self-illuminating pixels for a new display generation

There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?

At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...

Im Focus: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

Im Focus: Dozens of binaries from Milky Way's globular clusters could be detectable by LISA

Next-generation gravitational wave detector in space will complement LIGO on Earth

The historic first detection of gravitational waves from colliding black holes far outside our galaxy opened a new window to understanding the universe. A...

Im Focus: Entangled atoms shine in unison

A team led by Austrian experimental physicist Rainer Blatt has succeeded in characterizing the quantum entanglement of two spatially separated atoms by observing their light emission. This fundamental demonstration could lead to the development of highly sensitive optical gradiometers for the precise measurement of the gravitational field or the earth's magnetic field.

The age of quantum technology has long been heralded. Decades of research into the quantum world have led to the development of methods that make it possible...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

 
Latest News

Research reveals how order first appears in liquid crystals

23.05.2018 | Life Sciences

Space-like gravity weakens biochemical signals in muscle formation

23.05.2018 | Life Sciences

NIST puts the optical microscope under the microscope to achieve atomic accuracy

23.05.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>