Tag Archives: Cooper Pairs

‘Superconductivity: The Musical!’ wins the 2018 Dance Your Ph.D. competition

I can’t believe that October 24, 2011 was the last time the Dance Your Ph.D. competition was featured here. Time flies, eh? Here’s the 2018 contest winner’s submission, Superconductivity: The Musical!, (Note: This video is over 11 mins. long),

A February 17, 2019 CBC (Canadian Broadcasting Corporation) news item introduces the video’s writer, producer,s musician, and scientist,

Swing dancing. Songwriting. And theoretical condensed matter physics.

It’s a unique person who can master all three, but a University of Alberta PhD student has done all that and taken it one step further by making a rollicking music video about his academic pursuits — and winning an international competition for his efforts.

Pramodh Senarath Yapa is the winner of the 2018 Dance Your PhD contest, which challenges scientists around the world to explain their research through a jargon-free medium: dance.

The prize is $1,000 and “immortal geek fame.”

Yapa’s video features his friends twirling, swinging and touch-stepping their way through an explanation of his graduate research, called “Non-Local Electrodynamics of Superconducting Wires: Implications for Flux Noise and Inductance.”

Jennifer Ouelette’s February 17, 2019 posting for the ars Technica blog offers more detail (Note: A link has been removed),

Yapa’s research deals with how matter behaves when it’s cooled to very low temperatures, when quantum effects kick in—such as certain metals becoming superconductive, or capable of conducting electricity with zero resistance. That’s useful for any number of practical applications. D-Wave Systems [a company located in metro Vancouver {Canada}], for example, is building quantum computers using loops of superconducting wire. For his thesis, “I had to use the theory of superconductivity to figure out how to build a better quantum computer,” said Yapa.

Condensed matter theory (the precise description of Yapa’s field of research) is a notoriously tricky subfield to make palatable for a non-expert audience. “There isn’t one unifying theory or a single tool that we use,” he said. “Condensed matter theorists study a million different things using a million different techniques.”

His conceptual breakthrough came about when he realized electrons were a bit like “unsociable people” who find joy when they pair up with other electrons. “You can imagine electrons as a free gas, which means they don’t interact with each other,” he said. “The theory of superconductivity says they actually form pairs when cooled below a certain temperature. That was the ‘Eureka!’ moment, when I realized I could totally use swing dancing.”

John Bohannon’s Feb. 15, 2019 article for Science (magazine) offers an update on Yapa’s research interests (it seems that Yapa was dancing his Masters degree) and more information about the contest itself ,


“I remember hearing about Dance Your Ph.D. many years ago and being amazed at all the entries,” Yapa says. “This is definitely a longtime dream come true.” His research, meanwhile, has evolved from superconductivity—which he pursued at the University of Victoria in Canada, where he completed a master’s degree—to the physics of superfluids, the focus of his Ph.D. research at the University of Alberta.

This is the 11th year of Dance Your Ph.D. hosted by Science and AAAS. The contest challenges scientists around the world to explain their research through the most jargon-free medium available: interpretive dance.

“Most people would not normally think of interpretive dance as a tool for scientific communication,” says artist Alexa Meade, one of the judges of the contest. “However, the body can express conceptual thoughts through movement in ways that words and data tables cannot. The results are both artfully poetic and scientifically profound.”

Getting back to the February 17, 2019 CBC news item,

Yapa describes his video, filmed in Victoria where he earned his master’s degree, as a “three act, mini-musical.”

“I envisioned it as talking about the social lives of electrons,” he said. “The electrons starts out in a normal metal, at normal temperatures….We say these electrons are non-interacting. They don’t talk to each other. Electrons ignore each other and are very unsociable.”

The electrons — represented by dancers wearing saddle oxfords, poodle skirts, vests and suspenders — shuffle up the dance floor by themselves.

In the second act, the metal is cooled.

“The electrons become very unhappy about being alone. They want to find a partner, some companionship for the cold times,” he said

That’s when the electrons join up into something called Cooper pairs.

The dancers join together, moving to lyrics like, “If we peek/the Coopers are cheek-to-cheek.

In the final act, Yapa gets his dancers to demonstrate what happens when the Cooper pairs meet the impurities of the materials they’re moving in. All of a sudden, a group of black-leather-clad thugs move onto the dance floor.

“The Cooper pairs come dancing near these impurities and they’re like these crotchety old people yelling and shaking their fists at these young dancers,” Yapa explained.

Yapa’s entry to the annual contest swept past 49 other contestants to earn him the win. The competition is sponsored by Science magazine and the American Association for the Advancement of Science.

Congratulations to Pramodh Senarath Yapa.

Superconductivity with spin

Vivid lines of light tracing a pattern reminiscent of a spinning top toy Courtesy: Harvard University

Vivid lines of light tracing a pattern reminiscent of a spinning top toy Courtesy: Harvard University

An Oct. 14, 2016 Harvard University John A. Paulson School of Engineering and Applied Sciences (SEAS) press release (also on EurekAlert) by Leah Burrows describes how scientists have discovered a way to transmit spin information through supercapacitors,

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. Their breakthrough solves one the main challenges to quantum computing: how to transmit spin information through superconducting materials.

Every electronic device — from a supercomputer to a dishwasher — works by controlling the flow of charged electrons. But electrons can carry so much more information than just charge; electrons also spin, like a gyroscope on axis.

Harnessing electron spin is really exciting for quantum information processing because not only can an electron spin up or down — one or zero — but it can also spin any direction between the two poles. Because it follows the rules of quantum mechanics, an electron can occupy all of those positions at once. Imagine the power of a computer that could calculate all of those positions simultaneously.

A whole field of applied physics, called spintronics, focuses on how to harness and measure electron spin and build spin equivalents of electronic gates and circuits.

By using superconducting materials through which electrons can move without any loss of energy, physicists hope to build quantum devices that would require significantly less power.

But there’s a problem.

According to a fundamental property of superconductivity, superconductors can’t transmit spin. Any electron pairs that pass through a superconductor will have the combined spin of zero.

In work published recently in Nature Physics, the Harvard researchers found a way to transmit spin information through superconducting materials.

“We now have a way to control the spin of the transmitted electrons in simple superconducting devices,” said Amir Yacoby, Professor of Physics and of Applied Physics at SEAS and senior author of the paper.

It’s easy to think of superconductors as particle super highways but a better analogy would be a super carpool lane as only paired electrons can move through a superconductor without resistance.

These pairs are called Cooper Pairs and they interact in a very particular way. If the way they move in relation to each other (physicists call this momentum) is symmetric, then the pair’s spin has to be asymmetric — for example, one negative and one positive for a combined spin of zero. When they travel through a conventional superconductor, Cooper Pairs’ momentum has to be zero and their orbit perfectly symmetrical.

But if you can change the momentum to asymmetric — leaning toward one direction — then the spin can be symmetric. To do that, you need the help of some exotic (aka weird) physics.

Superconducting materials can imbue non-superconducting materials with their conductive powers simply by being in close proximity. Using this principle, the researchers built a superconducting sandwich, with superconductors on the outside and mercury telluride in the middle. The atoms in mercury telluride are so heavy and the electrons move so quickly, that the rules of relativity start to apply.

“Because the atoms are so heavy, you have electrons that occupy high-speed orbits,” said Hechen Ren, coauthor of the study and graduate student at SEAS. “When an electron is moving this fast, its electric field turns into a magnetic field which then couples with the spin of the electron. This magnetic field acts on the spin and gives one spin a higher energy than another.”

So, when the Cooper Pairs hit this material, their spin begins to rotate.

“The Cooper Pairs jump into the mercury telluride and they see this strong spin orbit effect and start to couple differently,” said Ren. “The homogenous breed of zero momentum and zero combined spin is still there but now there is also a breed of pairs that gains momentum, breaking the symmetry of the orbit. The most important part of that is that the spin is now free to be something other than zero.”

The team could measure the spin at various points as the electron waves moved through the material. By using an external magnet, the researchers could tune the total spin of the pairs.

“This discovery opens up new possibilities for storing quantum information. Using the underlying physics behind this discovery provides also new possibilities for exploring the underlying nature of superconductivity in novel quantum materials,” said Yacoby.

Here’s a link to and a citation for the paper,

Controlled finite momentum pairing and spatially varying order parameter in proximitized HgTe quantum wells by Sean Hart, Hechen Ren, Michael Kosowsky, Gilad Ben-Shach, Philipp Leubner, Christoph Brüne, Hartmut Buhmann, Laurens W. Molenkamp, Bertrand I. Halperin, & Amir Yacoby. Nature Physics (2016) doi:10.1038/nphys3877 Published online 19 September 2016

This paper is behind a paywall.