Cutting corners to make superconductors work better

Feb 14, 2012
Cutting corners to make superconductors work better
Making superconducting nanocircuits with rounded corners will improve their performance.

Making superconducting nanocircuits with rounded corners will improve their performance, according to John R. Clem, a physicist at the U.S. Department of Energy’s Ames Laboratory, and Karl K. Berggren, an associate professor of electrical engineering at the Massachusetts Institute of Technology.

Clem and Berggren calculated the critical current in thin and narrow superconducting strips with sharp right-angle turns, 180-degree turnarounds, and more complicated geometries. They found that current crowding, which occurs at the inner corners when the current rounds sharp turns, significantly reduces the current where a voltage first appears, called the critical current. Rounded corners, according to Clem and Berggren, will significantly improve critical currents.

The new theoretical work explains existing experimental measurements of critical currents that had previously not been understood.

“These results may help improve fundamental measurements of the critical currents of thin and narrow strips, because many previous experiments, which used samples with sharp corners, are likely to have yielded anomalously low values of the critical current because of current crowding,” said Clem.

The results may also have applications in the design of the meander lines in superconducting nanowire single-photon detectors, which perform best when the lines have the highest possible critical currents, as well as in quantum gates for quantum computers, terahertz detectors for astronomy, and SQUID magnetometers used to measure extremely small magnetic fields.

“We’ve known for some time that patterns with extremely sharp hairpin turns exhibit reduced critical current,” said Berggren, “but now we finally understand why this happens, and can eliminate this problem in our future detector designs. The result is likely to be detectors with improved efficiency and reduced noise.”

The research was done while Berggren was on sabbatical at the Technical University of Delft in the Netherlands.The work at Ames Laboratory was funded by the DOE’s Office of Science’s Office of Basic Energy Sciences.

Explore further: Finding the 'heart' of an obstacle to superconductivity

More information: A paper describing both the theoretical calculations and a comparison with experiment recently appeared in Physical Review B: link.aps.org/doi/10.1103/PhysRevB.84.174510 .

add to favorites email to friend print save as pdf

Related Stories

Recommended for you

Unleashing the power of quantum dot triplets

3 hours ago

Quantum computers have yet to materialise. Yet, scientists are making progress in devising suitable means of making such computers faster. One such approach relies on quantum dots—a kind of artificial atom, ...

Chemist develops X-ray vision for quality assurance

3 hours ago

It is seldom sufficient to read the declaration of contents if you need to know precisely what substances a product contains. In fact, to do this you need to be a highly skilled chemist or to have genuine ...

The future of ultrashort laser pulses

3 hours ago

Rapid advances in techniques for the creation of ultra-short laser pulses promise to boost our knowledge of electron motions to an unprecedented level.

IHEP in China has ambitions for Higgs factory

21 hours ago

Who will lay claim to having the world's largest particle smasher?. Could China become the collider capital of the world? Questions tease answers, following a news story in Nature on Tuesday. Proposals for ...

The physics of lead guitar playing

22 hours ago

String bends, tapping, vibrato and whammy bars are all techniques that add to the distinctiveness of a lead guitarist's sound, whether it's Clapton, Hendrix, or BB King.

User comments : 0