Atomic-scale details of electron distribution reveal a novel mechanism for current to flow without energy loss.
Image courtesy of Brookhaven National Laboratory
Electron density distribution (indicated by both the blue and red, as areas of deficiency and excess of electrons, respectively) in barium iron arsenide for undoped/nonsuperconducting and doped/superconducting alloys. There is a remarkable increase in charge distribution around iron (Fe) and arsenic (As) atoms in the superconducting material.
Newswise — Electric current flows without any resistance in a superconducting state thanks to a surprising redistribution of bonding electrons and the associated electronic and atomic behavior after substitution of some cobalt atoms for iron in barium iron arsenide.
This discovery of substitution-induced charge redistribution demonstrates the prominent role of bonding (and the associated electron fluctuations) in the emergence of superconductivity in iron-based alloys. It suggests a new route for finding higher performance superconductors through engineering and optimization of the electron density among the atoms in the material.
The flow of current in ordinary metals and other materials that conduct electricity is composed of electrons; however, the charge carriers are scattered when they conduct electricity, resulting in dissipation and energy loss, typically in the form of heat.
In a superconductor, the electrons form into pairs that allow them to move through the material without resistance, eliminating the energy lost and thus increasing the efficient use of electricity. The challenge in creating such electron pairs is overcoming the natural tendency for electrons to repel each other. One solution is to utilize electronic polarizability that can yield an attractive interaction between electrons, thus allowing pair formation and the potential for loss-free current flow.
Such a mechanism was proposed almost five decades ago, but it was never experimentally verified. Using electron diffraction with subatomic precision, scientists at Brookhaven National Laboratory have mapped out the redistribution of orbital electrons in barium iron arsenide, with and without cobalt substitution. The results reveal a remarkable increase in charge distribution around the iron and arsenic atoms as cobalt is incorporated into the material.
Electron energy loss spectroscopy was carried out to determine the charge carrier-injection effect of cobalt substitution, while density functional theory was used to model electronic and atomic behavior. The induced charge redistribution around the iron and arsenic atoms after cobalt substitution suggests that the strongly coupled bond-electron fluctuation and charge separation may provide a new mechanism for high-temperature superconductivity. These results may guide the design of new superconductors.
DOE Office of Science, Basic Energy Sciences provided primary support for the research at Brookhaven National Laboratory. The Chinese National Science Foundation supported the sample synthesis at the Institute of Physics, Chinese Academy of Sciences.
C. Ma, L. Wu, W.G. Yin, H. Yang, H. Shi, Z. Wang, J. Li, C. C. Homes, Y. Zhu, “Strong coupling of the iron-quadrupole and anion-dipole polarizations in Ba(Fe1−xCox)2As2.” Physical Review Letters 112, 077001 (2014). [DOI: 10.1103/PhysRevLett.112.077001]
Kristin Manke | newswise
How protons move through a fuel cell
22.06.2017 | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt
Fraunhofer IZFP acquires lucrative EU project for increasing nuclear power plant safety
21.06.2017 | Fraunhofer-Institut für Zerstörungsfreie Prüfverfahren IZFP
An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.
Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...
Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.
Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...
Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.
As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...
Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.
With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...
Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine
Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...
19.06.2017 | Event News
13.06.2017 | Event News
13.06.2017 | Event News
23.06.2017 | Physics and Astronomy
23.06.2017 | Physics and Astronomy
23.06.2017 | Information Technology