Cutting corners to make superconductors work better

February 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: Key ingredient: Change in material boosts prospects of ultrafast single-photon detector

More information: A paper describing both the theoretical calculations and a comparison with experiment recently appeared in Physical Review B: .

Related Stories

Recommended for you

CERN collides heavy nuclei at new record high energy

November 25, 2015

The world's most powerful accelerator, the 27 km long Large Hadron Collider (LHC) operating at CERN in Geneva established collisions between lead nuclei, this morning, at the highest energies ever. The LHC has been colliding ...

'Material universe' yields surprising new particle

November 25, 2015

An international team of researchers has predicted the existence of a new type of particle called the type-II Weyl fermion in metallic materials. When subjected to a magnetic field, the materials containing the particle act ...

Exploring the physics of a chocolate fountain

November 24, 2015

A mathematics student has worked out the secrets of how chocolate behaves in a chocolate fountain, answering the age-old question of why the falling 'curtain' of chocolate surprisingly pulls inwards rather than going straight ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.