International Team Unlocks Insights Into High-Temperature Superconductivity

An international research team at BESSY II has made significant strides in understanding high-temperature superconductivity by measuring the energy of charge carrier pairs in undoped La2CuO4. Their findings indicate that interaction energies within the copper oxide layers, which have potential superconducting properties, are considerably lower than those in the insulating lanthanum oxide layers. This research, published in the journal Nature Communications, could provide crucial insights into other functional materials as well.

The phenomenon of high-temperature superconductivity, which allows materials to conduct electricity without loss, was first identified approximately 40 years ago. Unlike traditional superconductors, which require temperatures close to absolute zero, high-temperature superconductors operate at higher, yet still sub-room temperature levels. Despite their practical applications, the underlying mechanisms remain elusive.

The research, led by Professor Alexander Föhlisch, utilized samples from the University of Rome. These samples consist of alternating layers of copper and lanthanum oxide, specifically formulated as La2CuO4. When doped with foreign atoms, this compound can exhibit superconductivity below 40 Kelvin, with the superconducting activity localized in the CuO layers while the LaO layers stay insulating.

In their experiment, the researchers sought to understand the strength of interactions between charge carriers in the different oxide layers. According to Dr. Danilo Kühn, the first author of the study, the measurements were conducted at room temperature, focusing on the interactions between charge carriers around oxygen atoms.

The team employed a sophisticated method known as Auger photoelectron coincidence spectroscopy, utilizing time-of-flight spectrometers with a distinctive configuration. They directed special X-ray pulses at the sample, allowing them to monitor interaction processes occurring at an extremely rapid pace. This innovative approach enabled precise analysis of interactions specifically within the copper oxide layer, which is integral to superconductivity.

The results revealed that interaction energies in the copper oxide layer were significantly lower than in the insulating lanthanum oxide. “These findings enhance our understanding of the mechanisms underlying high-temperature superconductivity,” stated Föhlisch. He also noted that this measurement technique might shed light on the properties of other functional materials, expanding the potential applications of this research.

The study brings the scientific community closer to deciphering the complex behaviors associated with high-temperature superconductors, a field that continues to intrigue researchers worldwide. Further investigations could lead to advancements in technology and materials science, as understanding these interactions opens the door to new possibilities in superconducting applications.

For more detailed information, refer to the original research article by Danilo Kühn et al. titled “Direct observation of the on-site oxygen 2p two-hole Coulomb energy in La2CuO4,” available in Nature Communications (2025).