This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Superconductors are materials that carry electricity with zero resistance below specific temperatures. Many of these materials become superconducting at very low temperatures, yet some enter superconducting phases at higher temperatures.
While high-temperature superconductivity has been widely studied over the past few decades, its underlying physical processes have not yet been clearly elucidated. In some high-temperature superconductors, holes (i.e., electron vacancies) can organize themselves into stripes. Researchers at the Beijing Computational Science Research Center, Beijing Normal University and Chongqing University recently investigated the possible contribution of this stripe organization to d-wave pairing, in which paired electrons have a quantum wave pattern that changes sign between perpendicular directions and is often represented as a four-lobed cloverleaf shape.
Their paper, published in Physical Review Letters, offers a possible new explanation for how electron pairing could emerge around stripes in models of strongly correlated, hole-doped materials. "In 2005, Science Magazine listed the mechanism of high-temperature superconductivity as one of the 100 most important unanswered questions in science," Xue-Feng Zhang, senior author of the paper, told Phys.org. "It appeared again in their 2021 '125 Questions' collection.
That tells you how stubborn this puzzle is. My collaborators and I have been obsessed with it since 2023." Earlier experiments and numerical simulations suggested a close relationship between superconductivity and stripes in cuprates, copper-oxide materials containing layers of copper and oxygen atoms. Calculations indicated that in models of these materials, electron pairs tend to accumulate along hole-rich stripes.
Physicist Jan Zaanen described these stripes as "rivers of charge" separated by insulating regions. "Looking at a stripe and seeing pairing is like hearing an orchestra and knowing the melody is beautiful, without knowing which instrument is playing it," said Zhang. "Our objective was simple but terrifying: look inside the stripe and identify the musician." An emerging technique called quantum gas microscopy opened new possibilities for studying strongly interacting quantum systems and their underlying physics.
This technique essentially allows experimental physicists to take actual photographs of individual atoms in optical lattices. "We asked ourselves: can we do the same thing with our numerical wavefunctions?" said Zhang. "If we could take a high-resolution snapshot of a stripe, maybe we could finally catch the pairing mechanism in the act." As part of their study, Zhang and his colleagues decided to study two specific models describing how strongly interacting electrons behave in lattice materials.
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