Nav: Home

Stressing metallic material controls superconductivity

October 14, 2019

No strain, no gain - that's the credo for Cornell researchers who have helped find a way to control superconductivity in a metallic material by stressing and deforming it.

The researchers, led by Katja Nowack, assistant professor of physics in the College of Arts and Sciences, collaborated with a team led by Philip Moll from the Institute of Material Science and Engineering at École Polytechnique Fédéral de Lausanne in Switzerland. Their paper, "Spatial Control of Heavy-Fermion Superconductivity in CeIrIn5," published Oct. 11 in Science.

The project began as a puzzle. Moll's team had been measuring superconductivity in microstructure devices made from cerium iridium indium-5 (CeIrIn5), a heavy fermion metal. The team was perplexed to find that the device's critical temperature - the point at which electrical resistance vanishes and superconductivity occurs, also known as the transition temperature - changed when the devices were measured in different configurations. Typically, the critical temperature should be the same throughout the structure.

Moll's frequent collaborator, Brad Ramshaw, Cornell assistant professor of physics and a co-author of the paper, told Nowack about the results, and Nowack decided to investigate the issue. Her lab had constructed a scanning probe microscope for highly sensitive magnetic imaging that operates at temperatures as low as 10 millikelvin (approximately minus 459 degrees Fahrenheit) and is ideally suited for imaging the structures Moll was studying. The probes are superconducting quantum interference devices, or SQUIDs.

When Nowack and her team imaged the small structures, they realized that deformations in the material were enabling the superconductivity to form in a spatially patterned way.

"The pattern we observed looked like something was pulling on the four corners of the square-shaped sample," Nowack said.

To fabricate the devices, Moll's team had glued CeIrIn5 crystal structures to a layer of sapphire and patterned them with a focus ion beam, which functions like a miniature sandblaster. Like most metals, CeIrIn5 contracts when cooled. But sapphire, an insulator, hardly shrinks at all. When the two materials were cooled together, the CeIrIn5was deformed by the mechanical tension between the two layers.

"The critical temperature in CeIrIn5 responds to strain," Nowack said. "So pulling on the crystal in one direction will make that temperature go a little higher, and then pulling on the crystal in another direction will make it go lower."

These strains can shift the superconducting transition temperature by nearly a factor of four, from approximately 200 to 800 millikelvin.

"The structures have trenches and features cut into them with high spatial control," Nowack said. "All those details in the geometry heavily influence how the deformation looks at the end. This is really exciting because by modifying the geometry, we can spatially control the superconductivity in these little structures accordingly."

Using this method allows the researchers to modulate superconductivity without relying on chemical augmentation, known as doping, which can compromise how clean the crystal is and its electronic properties.

"Now that we understand how to use microstructuring to tune the electronic properties of CeIrIn5, we can extend our approach to other materials, or we can design more sophisticated structures and fine-tune our control over the superconducting transition in heavy fermion compounds," said doctoral student Matt Ferguson, who performed the imaging and served as co-lead author along with Maja Bachmann from the Max Planck Institute in Germany and the University of St. Andrews, Scotland.

"In addition, we want to see if we can do something similar to other types of electronic order, such as magnetism," Nowack said.

One of the most immediate applications, according to Nowack, is the creation of so-called Josephson junction devices, which are essentially "superconductor sandwiches" - thin insulators or metals tucked between two superconductors that can enable nonlinear electrical behavior. Josephson junctions are the building blocks of superconducting logic and quantum circuits, which may provide a big boost for high-speed electronics and computing in the future.

A Josephson junction based on this work would be made within the same clean piece of crystal, with the thin metallic section created through focused strain.

"Sometimes stressing can produce amazing results," Nowack said.
Co-authors include doctoral students David Low, Sayak Ghosh and Florian Theuss, and researchers at the Max Planck Institute for Chemical Physics of Solids; University of St. Andrews; Los Alamos National Laboratory, New Mexico; and Technical University Dresden, Germany.

The Cornell research was primarily supported by the U.S. Department of Energy, and the Cornell Center for Materials Research, with funding from the National Science Foundation's Materials Research Science and Engineering Center.

Cornell University

Related Superconductivity Articles:

How a magnet could help boost understanding of superconductivity
Physicists have unraveled a mystery behind the strange behavior of electrons in a ferromagnet, a finding that could eventually help develop high temperature superconductivity.
New study explains why superconductivity takes place in graphene
Theoretical physicists take important step in development of high temperature superconductors.
Better studying superconductivity in single-layer graphene
A new study published in EPJ B demonstrates that an existing technique is better suited for probing superconductivity in pure, single-layer graphene than previously thought.
Stressing metallic material controls superconductivity
No strain, no gain -- that's the credo for Cornell researchers who have helped find a way to control superconductivity in a metallic material by stressing and deforming it.
First report of superconductivity in a nickel oxide material
Scientists at SLAC and Stanford have made the first nickel oxide material that shows clear signs of superconductivity - the ability to transmit electrical current with no loss.
A hallmark of superconductivity, beyond superconductivity itself
Physicists have found 'electron pairing,' a hallmark feature of superconductivity, at temperatures and energies well above the critical threshold where superconductivity occurs.
Manipulating superconductivity using a 'mechanic' and an 'electrician'
Strongly correlated materials can change their resistivity from infinity to zero with minute changes in conditions.
Triplet superconductivity demonstrated under high pressure
Researchers in France and Japan have demonstrated a theoretical type of unconventional superconductivity in a uranium-based material, according to a study published in the journal Physical Review Letters.
The mechanism of high-temperature superconductivity is found
Russian physicist Viktor Lakhno from Keldysh Institute of Applied Mathematics, RAS considers symmetrical bipolarons as a basis of high-temperature superconductivity.
Superconductivity is heating up
Theory suggests that metallic hydrogen should be a superconductor at room temperature; however, this material has yet to be produced in the lab.
More Superconductivity News and Superconductivity Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Reinvention
Change is hard, but it's also an opportunity to discover and reimagine what you thought you knew. From our economy, to music, to even ourselves–this hour TED speakers explore the power of reinvention. Guests include OK Go lead singer Damian Kulash Jr., former college gymnastics coach Valorie Kondos Field, Stockton Mayor Michael Tubbs, and entrepreneur Nick Hanauer.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at