Tuning the bonds of paired quantum particles to create dissipationless flow

The underlying theory is simple enough. "If you can get electrons to pair, they can superconduct," said Dean. According to the Bardeen-Cooper-Schrieffer (BCS) theory, an attractive force between electrons—no matter how weak—will cause those electrons to pair up and form a new kind of particle called a "Cooper pair." These behave like particles called bosons and, at low enough temperatures, can enter into a collective state and move through a material unimpeded by disorder—a feature any single electron just cannot achieve on its own.

But there's been a problem. "Electrons do not want to pair," said Dean. Like repels like, as the saying goes. Rather than trying to force a bond between two negatively charged electrons, the team has been exploring how opposites can attract to yield an equivalent 'paired' boson.

The general idea, which was first proposed by theoretical physicists, is now being realized by the team in atom-thin sheets of graphene, a material with unique properties that they have been working to leverage for several years. Depending on the voltages and magnetic fields applied, graphene sheets can be made that are populated with either negatively charged electrons or with positively charged holes. When two such sheets are put together, electrons on one sheet will want to pair with oppositely charged holes on the other, forming the bosonic pair.

Electrons and holes don't just need to interact with each other; the bosonic pairs they form also need to interact with other pairs to reach a collective quantum condensate state. By tweaking the number of insulating layers, the team could control the binding strength between the electrons and holes, while changing the external magnetic field adjusted the interaction between bosonic pairs.

[snip] The underlying theory is simple enough. "If you can get electrons to pair, they can superconduct," said Dean. According to the Bardeen-Cooper-Schrieffer (BCS) theory, an attractive force between electrons—no matter how weak—will cause those electrons to pair up and form a new kind of particle called a "Cooper pair." These behave like particles called bosons and, at low enough temperatures, can enter into a collective state and move through a material unimpeded by disorder—a feature any single electron just cannot achieve on its own. But there's been a problem. "Electrons do not want to pair," said Dean. Like repels like, as the saying goes. Rather than trying to force a bond between two negatively charged electrons, the team has been exploring how opposites can attract to yield an equivalent 'paired' boson. [/snip]

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Thanks BenLurkin.

BTW, Bardeen also shared the Nobel in physics for his work on the discovery of the transistor. He's the only double winner of the physics Nobel.

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