Nav: Home

Superconductivity in an alloy with quasicrystal structure

March 26, 2018

Nagoya, Japan - Extraordinary things happen at low temperatures. One of the best examples is surely superconductivity. This phenomenon, wherein the electrical resistance of a solid drops to zero below a critical temperature, has been known for a century, and now has applications in science and industry. Physics and chemistry students can even make their own levitating magnets from superconducting alloys.

Most superconductors, like most solids, are crystalline: their atomic structures are built from periodically repeating cells. Since the 1980s an alternative form of solid, the quasicrystal (QC), has become prominent. Although QCs have symmetry, like crystals, they have no repeat units. This lack of periodicity results in unusual electronic structures. Now, in a study in Nature Communications, a research team led by Nagoya University has discovered superconductivity in a QC for the first time.

The team studied an alloy of aluminum, zinc and magnesium. The crystalline version is known to be superconducting. However, the structure of Al-Zn-Mg depends on the ratio of the three elements. The team found that Al had a crucial effect on the alloy's properties. As study first author Keisuke Kamiya notes, "When we reduced the Al content while keeping the Mg content almost constant, the critical temperature for superconductivity at first decreased gradually from ~0.8 to ~0.2 K. However, at 15% Al, two things happened: the alloy transformed into a quasicrystal, and the critical temperature plummeted to ~0.05 K."

This extremely low critical temperature, just 1/20 of a degree above absolute zero, explains why superconductivity in QCs has proven so hard to achieve. Nonetheless, the QC alloy showed two archetypal features of superconductors: a jump in specific heat at the critical temperature, and the almost total exclusion of magnetic flux from the interior, known as the Meissner effect.

Superconduction in conventional crystals is now well-understood. At sufficiently low temperature, the negatively charged electrons overcome their mutual repulsion and attract one another, teaming up into pairs. These "Cooper pairs" coalesce into a Bose-Einstein condensate, a quantum state of matter with zero electrical resistance. However, the attraction between electrons relies on their interaction with the solid lattice, and conventional theory assumes this is a periodic crystal, rather than a QC.

For the origin of superconduction in the QC alloy, the team considered three possibilities. The most exotic was "critical eigenstates": special electronic states only found near absolute zero. The electronic eigenstates are extended in crystals, and localized in random solids, but the spatial extent of the critical eigenstates in QCs--which are neither periodic nor random--is unclear. However, the team ruled them out based on their measurements. That led back to Cooper pairs, in either the extended or the less-common "weak-coupling" variety. In fact, the alloy closely resembled a typical weak-coupling superconductor.

"It's interesting that the superconductivity of this alloy was not linked to its quasicrystallinity, but resembled that in so-called dirty crystals," says corresponding author Noriaki K. Sato. "However, the theory of quasicrystals also predicts another form of superconduction, based on fractal geometry in QCs. We believe there is a strong possibility that fractal superconductivity makes at least some contribution, and we would be excited to finally measure it."

The article, "Discovery of superconductivity in quasicrystal," was published in Nature Communications at DOI:10.1038/s41467-017-02667-x.

Nagoya University

Related Superconductivity Articles:

Looking at light to explore superconductivity in boron-diamond films
More than a decade ago, researchers discovered that when they added boron to the carbon structure of diamond, the combination was superconductive.
Discovery in new material raises questions about theoretical models of superconductivity
The US Department of Energy's Ames Laboratory has successfully created the first pure, single-crystal sample of a new iron arsenide superconductor, CaKFe4As4, and studies of this material have called into question some long-standing theoretical models of superconductivity.
Superconductivity with two-fold symmetry -- new evidence for topological superconductor SrxBi2Se3
Topological superconductivity is the quantum condensate of paired electrons with an odd parity of the pairing function.
Portable superconductivity systems for small motors
Superconductivity is one of modern physics' most intriguing scientific discoveries.
Graphene's sleeping superconductivity awakens
The intrinsic ability of graphene to superconduct (or carry an electrical current with no resistance) has been activated for the first time.
Superconductivity of pure Bismuth crystal at 0.00053 K
Scientists at TIFR Mumbai have discovered superconductivity of pure Bismuth crystal.
When crystal vibrations' inner clock drives superconductivity
Superconductivity is like an Eldorado for electrons, as they flow without resistance through a conductor.
Physicists induce superconductivity in non-superconducting materials
Researchers at the University of Houston have reported a new method for inducing superconductivity in non-superconducting materials, demonstrating a concept proposed decades ago but never proven.
A new spin on superconductivity
Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have made a discovery that could lay the foundation for quantum superconducting devices.
Superconductivity: After the scenario, the staging
Superconductivity with a high Tc continues to present a theoretical mystery.

Related Superconductivity Reading:

Superconductivity: A Very Short Introduction
by Stephen J. Blundell (Author)

Superconductivity, Third Edition (Elsevier Insights)
by Charles P. Poole Jr. (Author), Horacio A. Farach (Author), Richard J. Creswick (Author), Ruslan Prozorov (Author)

Introduction to Superconductivity: Second Edition (Dover Books on Physics) (Vol i)
by Michael Tinkham (Author)

Superconductivity: An Introduction
by Reinhold Kleiner (Author), Werner Buckel (Author), Rudolf Huebener (Translator)

Superconductivity, Superfluids, and Condensates (Oxford Master Series in Physics)
by James F. Annett (Author)

by The Open University

Theory Of Superconductivity (Advanced Books Classics)
by J. Robert Schrieffer (Author)

by Cambridge University Press

Superconductivity: Fundamentals and Applications (Physics)
by Werner Buckel (Author), Reinhold Kleiner (Author)

Superconductivity: The Next Revolution?
by Gianfranco Vidali (Author)

Best Science Podcasts 2018

We have hand picked the best science podcasts for 2018. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Why We Hate
From bullying to hate crimes, cruelty is all around us. So what makes us hate? And is it learned or innate? This hour, TED speakers explore the causes and consequences of hate — and how we can fight it. Guests include reformed white nationalist Christian Picciolini, CNN commentator Sally Kohn, podcast host Dylan Marron, and writer Anand Giridharadas.
Now Playing: Science for the People

#483 Wild Moms
This week we're talking about what it takes to be a mother in the wild, and how how human moms compare to other moms in the animal kingdom. We're spending an hour with Dr. Carin Bondar, prolific science communicator and author. We'll be discussing a myriad of stories from her latest book, "Wild Moms: Motherhood in the Animal Kingdom", covering the exciting, stressful and even sinister sides of motherhood.