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!
From ancient fossils to future cars
21.10.2016 | University of California - Riverside
Study explains strength gap between graphene, carbon fiber
20.10.2016 | Rice University
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.
"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...
COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.
In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...
'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.
Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
21.10.2016 | Health and Medicine
21.10.2016 | Information Technology
21.10.2016 | Materials Sciences