The results also suggest that vibrations (called phonons), within the lattice structure of these materials, are essential to their superconductivity by binding electrons in pairs. The research is published in the February 26 - March 2 on-line edition of the Proceedings of the National Academy of Sciences.
Superconductors are substances that conduct electricity — the flow of electrons — without any resistance. Electrical resistance disappears in superconductors at specific, so-called, transition temperatures, Tc's. The early conventional superconductors had to be cooled to extremely low (below 20 K or –253ºC) temperatures for electricity to flow freely. In 1986 scientists discovered a class of high-temperature superconductors made of ceramic copper oxides that have much higher transition temperatures. But understanding how they work and thus how they can be manipulated has been surprisingly hard.
As Carnegie's Xiao-Jia Chen, lead author of the study explains: "High-temperature superconductors consist of copper and oxygen atoms in a layered structure. Scientists have been trying hard to determine the properties that affect their transition temperatures since 1987. In this study, we found that by substituting oxygen-16 with its heavier sibling oxygen-18, the transition temperature changes; such a substitution is known as the isotope effect. The different masses of the isotopes cause a change in lattice vibrations and hence the binding force that enables pairs of electrons to travel through the material without resistance. Even more exciting is our discovery that manipulating the compression of the crystalline lattice of the high-Tc material has a similar effect on the superconducting transition temperature. Our study revealed that pressure and the isotope effect have equivalent roles on the transition temperature in cuprate superconductors."
Superconducting materials can achieve their maximum transition temperatures at a specific amount of "doping," which is simply the addition of charged particles (negatively charged electrons or positively charged holes). Both the transition temperature and isotope effect critically depend on the doping level. For optimally doped materials, the higher the maximum transition temperature is, the smaller the isotope effect is.
Understanding this behavior is very challenging. The Carnegie / Hong Kong collaboration found that if phonons are at work, they would account both for the magnitude of the isotope effect, as a function of the doping level, and the variation among different types of cuprate superconductors. The study also revealed what might be happening to modify the electronic structures among various optimally doped materials to cause the variation of the superconducting properties. The suite of results presents a unified picture for the oxygen isotope effect in cuprates at ambient condition and under high pressure.
"Although we've known for some time that vibrations of the atoms, or phonons, propel electrons through conventional superconductors, they have just recently been suspected to be at work in high-temperature superconductors," commented coauthor Viktor Struzhkin. "This research suggests that lattice vibrations are important to the way the high-Tc materials function as well. We are very excited by the possibilities arising from these findings."
Xiao-Jia Chen | EurekAlert!
An innovative high-performance material: biofibers made from green lacewing silk
20.01.2017 | Fraunhofer-Institut für Angewandte Polymerforschung IAP
Treated carbon pulls radioactive elements from water
20.01.2017 | Rice University
An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
19.01.2017 | Event News
10.01.2017 | Event News
09.01.2017 | Event News
20.01.2017 | Awards Funding
20.01.2017 | Materials Sciences
20.01.2017 | Life Sciences