Researchers have published a new theoretical framework.
Physicists have pinpointed a mechanism responsible for creating oscillating superconductivity called dual-density waves. Findings that shed light on an atypical high-temperature superconductor state observed in certain materials, such as high-temperature superconductors, Physical Review Letters.
“We discovered that structures known as Van Hove singularities can produce states of modulating, oscillating superconductivity,” says Luiz Santos, assistant professor of physics at Emory University and senior author of the study. “Our work provides a new theoretical framework for understanding the emergence of this behavior, which is a poorly understood phenomenon.”
The first author of the study is Emory physics graduate student Pedro Castro. Co-authors include Daniel Shaffer, a postdoctoral fellow in the Santos group, and Yi-Ming Wu of Stanford University.
Santos is a theorist specializing in condensed matter physics. He studies the interactions of quantum materials (small things like atoms, photons, and electrons) that don’t behave according to the laws of classical physics.
Superconductivity, or the ability of some materials to conduct electricity without loss of energy when cooled to a very low temperature, is an example of intriguing quantum behavior. The phenomenon was discovered in 1911 when Dutch physicist Heike Kamerlingh Onnes showed that mercury loses electrical resistance when cooled to 4 Kelvin, or minus 371 degrees Celsius. Fahrenheit. About this temperature UranusThe coldest planet in the solar system.
It took until 1957 for scientists to find an explanation for how and why superconductivity occurs. At normal temperatures, electrons circulate more or less independently. They collide with other particles, causing them to change velocity and direction and dissipate energy. However, at low temperatures, electrons can organize into a new state of matter.
“They form interconnected pairs in a collective situation that behaves like a single entity,” explains Santos. “You can think of them like soldiers in an army. It’s easier to deflect if they’re acting alone. But it’s much harder to destabilize them when they’re marching in the same stride. This collective state carries the current solidly.”
Superconductivity has great potential. Theoretically, it could allow electrical current to move without heating wires or losing energy. These wires can then carry much more electricity much more efficiently.
“One of the holy grails of physics is room temperature superconductivity, which is practical enough for everyday life applications,” says Santos. “This breakthrough could change the shape of civilization.”
Many physicists and engineers are working on this front to revolutionize how electricity is transmitted.
Meanwhile, superconductivity has already found application. Superconducting coils power electromagnets used in magnetic resonance imaging (MRI) machines for medical diagnostics. A handful of magnetic levitation trains are currently operating in the world, built on superconducting magnets that are 10 times stronger than ordinary electromagnets. The magnets repel each other when the mating poles face each other, creating a magnetic field that can lift and repel a train.
The Large Hadron Collider, a particle accelerator that scientists use to probe the fundamental structure of the universe, is another example of technology going through superconductivity.
Superconductivity continues to be discovered in more materials, including many that are superconducting at higher temperatures.
One of the focuses of Santos’ research is how interactions between electrons can lead to forms of superconductivity that could not be explained by the 1957 definition of superconductivity. An example of this so-called exotic phenomenon is oscillatory superconductivity, where paired electrons dance in waves by changing the amplitude.
In an unrelated project, Santos asked Castro to investigate certain properties of Van Hove singularities, that is, structures where many electronic states converge energetically. Castro’s project revealed that singularities appear to have the right kind of physics to seed oscillating superconductivity.
This encouraged Santos and his collaborators to dig deeper. They uncovered a mechanism that would allow these dancing-wave superconductivity states to emerge from Van Hove singularities.
“As theoretical physicists, we want to be able to predict and classify behavior to understand how nature works,” Santos says. “Then we can start asking questions of technological relevance.”
Some high-temperature superconductors that operate at temperatures about three times colder than a household freezer have this dancing wave behavior. The discovery of how this behavior might arise from Van Hove singularities provides a basis for experimenters to explore the world of possibilities it offers.
“I doubt that Kamerlingh Onnes thought about levitation or particle accelerators when he discovered superconductivity,” says Santos. “But everything we learn about the world has potential applications.”
Reference: Pedro Castro, Daniel Shaffer, Yi-Ming Wu, and Luiz H. Santos, 11 July 2023, by “Emergence of the Chern Supermetal and Pair-Density Wave through Higher-Order Van Hove Singularities in the Haldane-Hubbard Model” Physical Review Letters.
The study was funded by the U.S. Department of Energy’s Office of Basic Energy Sciences.
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