Researchers have uncovered a groundbreaking revelation about the origin of high-temperature superconductivity in copper oxide materials, potentially paving the way for more practical applications of this remarkable technology.
Unveiling the Hidden Order
Superconductors are a subject of such fascination that late-night television hucksters have made the idea of magnetic levitation so commonplace, one might almost forget there is technology at work behind those levitating frogs. Yet the copper oxide materials, or cuprates, that have been known for 33 years to exhibit high-temperature superconductivity, each time at a different material composition and with a different competitor metal substituting for copper than before, still lack any useful understanding of why they are superconductive.
Now, researchers at Okayama University in Japan believe the answer to those questions may lie in a new study — published July 3 in Nature Communications by associate professor Shinji Kawasaki and colleagues. A long-range charge density wave (CDW) order exists in an optimally doped Bi2201, a kind of the cuprate superconductor.
In an unconventional strategy, the researchers intentionally shattered the crystal symmetry of their copper oxide (CuO2) plane by placing it under uniaxial strain. This approach of inducing strain in the hope to access higher-quality samples enabled them to detect a covert long-range CDW order, akin to one thought to only exist within the under-doped regime in cuprates.
Synergistic Superconductivity and CDW
The researchers’ discovery raises a question to the common assumption that magnetism reigns supreme in copper oxides, and provides reference for future theoretical models trying to understand superconductivity.
The researchers found that the material underwent a drastic change — after straining it beyond 0.15%, the short-range CDW order turned into long-range CDW order. Increasing the strain further suppressed superconductivity while enhancing the CDW order, suggesting coexistence of both the long-range CDW and superconductivity in cuprate pseudogap state.
The finding could mean that the long-range CDW order which was thought to be limited to the low-doped regime is also present in a pseudogap state of cuprates, but being “hidden,” only reveals itself under strain. This result challenges the conventional wisdom and provides a new direction for investigating the mechanisms of high-temperature superconductivity.
Conclusion
This work is the significant milestone toward the understanding high-temperature superconductivity at order of magnitude higher energy scale in cuprate materials. The discovery of a latent long-range CDW order in the pseudogap state is thus a challenge to current paradigms and has important implications for the development of real-world superconducting materials. The discovery has many potential applications including improved power transmission, energy storage and medical imaging- all areas where the promise of superconducting technology could potentially provide significant benefits for the future of science and industry.
