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: How bubble studies benefit science and engineering

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

How bubble studies benefit science and engineering

44 minutes ago

The image above shows a perfect bubble imploding in weightlessness. This bubble, and many like it, are produced by the researchers from the École Polytechnique Fédérale de Lausanne in Switzerland. What ...

Famous Feynman lectures put online with free access

1 hour ago

(Phys.org) —Back in the early sixties, physicist Richard Feynman gave a series of lectures on physics to first year students at Caltech—those lectures were subsequently put into print and made into text ...

Single laser stops molecular tumbling motion instantly

5 hours ago

In the quantum world, making the simple atom behave is one thing, but making the more complex molecule behave is another story. Now Northwestern University scientists have figured out an elegant way to stop a molecule from ...

Ray tracing and beyond

Sep 01, 2014

Ray tracing is simple to explain at one level: "We all do it all day long: That's how you navigate the world visually," Gene Tracy explains. "The fact that I know that you're sitting there and not over there is because the ...

User comments : 0