Canadian researchers reveal hidden rivalry at heart of high-temperature superconductors
The study shows the pseudogap state emerges when superconductivity is suppressed, challenging previous theories about their relationship.
Researchers in Quebec have directly observed a competition between superconductivity and a mysterious quantum state in materials that could one day enable lossless electricity transmission.
The team from the Institut national de la recherche scientifique (INRS) used pulses of light to temporarily suppress superconductivity in copper-based compounds called cuprates, revealing the immediate emergence of a state known as the pseudogap.
"The pseudogap is one of the greatest mysteries in condensed-matter physics," said Professor Fabio Boschini, a specialist in ultrafast spectroscopy of quantum condensed matter at INRS.
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Boschini added that understanding its interaction with superconductivity is essential to explaining high-temperature superconductivity.
"Understanding how it interacts with superconductivity is essential if we want to explain why these materials can carry electricity without energy loss at unusually high temperatures," he said.
The findings, published in the journal Nature Physics, challenge the previous idea that the pseudogap might enable superconductivity.
Instead, the two states appear to actively suppress each other.
When superconductivity was suppressed using a pulse of light, the pseudogap immediately appeared, and the pseudogap diminished as superconductivity returned.
The observation was made possible by a time- and angle-resolved photoemission spectroscopy system at INRS's Advanced Laser Light Source laboratory.
"Thanks to the unique capabilities of the TR-ARPES system at the ALLS laboratory at INRS, we were able to directly observe what happens when superconductivity temporarily disappears and then re-emerges," said Dario Armanno, a PhD student at INRS and first author of the study.
"It is a bit like uncovering missing frames from a film that scientists have been trying to piece together for decades."
The technique allowed researchers to access previously hidden electronic states through this light-induced manipulation, providing a new window into the behavior of these complex materials.
The experiment not only confirmed the rivalry but also unveiled previously inaccessible electronic states.
Olivier Gingras, an associate research scientist at the Flatiron Institute's Center for Computational Quantum Physics, said the pseudogap and superconducting states in cuprates are among the most complex phenomena to reproduce theoretically.
"Our study reveals that they compete with one another and provides new insight into their behavior when both are excited simultaneously," Gingras said.
The research builds on the foundation laid by the 1986 discovery of cuprates, materials that hold the potential for lossless electricity transmission.
The precise mechanisms governing cuprate superconductivity remain a challenge, but this light-induced manipulation provides a clearer perspective for viewing the problem.
The findings have implications for the development of future quantum technologies and contribute to Canada's National Quantum Strategy.
The work was supported by funding from the Canada Foundation for Innovation's Major Science Initiatives Fund, the Alfred P. Sloan Foundation and the Natural Sciences and Engineering Research Council of Canada, among others.
With files from Quantum Zeitgeist