Since their discovery in 2008, a new class of superconductors has precipitated a flood of research the world over. Unlike the previously familiar copper ceramics (cuprates), the basic structure of this new class consists of iron compounds. Because the structure of these compounds differs from the cuprates in many fundamental ways, there is hope of gaining new insights into how the phenomenon of superconductivity arises.
Superconductors are generally produced by “doping” so-called parent compounds, which means introducing foreign atoms into them. There is a strong correlation between magnetism and superconductivity here – both being properties of solids. Conventional superconductors, such as those used in MRI machines in hospitals, do not like magnetism because it disturbs the interactions that lead to superconductivity within the crystal.
It is quite a different story for the celebrated high-temperature superconductors, such as cuprates and iron-arsenic compounds. In these cases, the magnetic forces actually help, even promote the onset of superconductivity. These compounds feature magnetic orders which, if they occur in a crystalline structure, are a telltale sign that the material is suitable to be a high-temperature superconductor.
With the new iron-based superconductors, it turns out that the symmetry of a magnetic order corresponds exactly to the symmetry in the superconductivity signal.
Dimitri Argyriou (HZB) and his colleagues have produced iron-tellurium-selenium crystals and determined their chemical composition using X-ray and neutron diffraction. They measured the magnetic signals in the crystals by performing neutron scattering experiments on the research reactor BER II of HZB and on the research reactor of the Institute Laue-Langevin in Grenoble.
They discovered that the symmetry of the magnetic order is significantly different from that of other iron-based parent compounds, such as iron-arsenic compounds. Yet, surprisingly, this difference has no impact on the development of superconductivity as a property. It has been detected that the magnetic signal caused by superconductivity - often referred to as the magnetic resonance - has the same symmetry as that of the magnetic order. And this is the same in all iron compounds, and apparently follows a universal mechanism that causes superconductivity for all of these materials.
Dimitri Argyriou describes this property as follows: “Going by what we know about the magnetic order of iron compounds, the iron-tellurium-selenium materials ought not to exhibit any superconductivity. But the opposite is the case: Despite the differences in magnetism, the signature of their superconductivity is the same. If we were now to understand how superconductivity arises in light of different starting conditions, then we could perhaps develop materials that are superconductive at even higher temperatures.”
Dr. Ina Helms | Helmholtz-Zentrum
The stacked colour sensor
16.11.2017 | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt
Counterfeits and product piracy can be prevented by security features, such as printed 3-D microstructures
16.11.2017 | Karlsruher Institut für Technologie (KIT)
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....
The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.
Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...
Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...
15.11.2017 | Event News
15.11.2017 | Event News
30.10.2017 | Event News
17.11.2017 | Physics and Astronomy
17.11.2017 | Health and Medicine
17.11.2017 | Studies and Analyses