Nagoya University-led team of physicists use a synchrotron radiation X-ray source to probe a so-called 'structure-less' transition and develop a new understanding of molecular conductors
We normally associate conduction of electricity with metals. However, some of the high measured conductivities are found in certain organic molecular crystals. Metallic, semiconducting and even superconducting properties can be achieved in these materials, which have interested scientists for decades.
Electron density distribution of the frontier orbital of a TMTTF molecule. Electrons of the constituent atoms of the molecule can be considered as either core electrons, which have no interactions with the surroundings, or electrons of frontier orbitals, which determine many physical properties of the molecule. We succeeded in visualizing the frontier molecular orbital distribution of a TMTTF by precise structural analysis using a core differential Fourier synthesis (CDFS) method.
Credit: Shunsuke Kitou
Changing temperature or pressure causes phase transitions in the crystal structure of molecular conductors and their related conduction properties. Scientists can usually determine the crystal structure using X-ray diffraction. However, structural change accompanying phase transition in a particular organic crystal (TMTTF)2PF6 has defied examination for almost 40 years.
Now, a research team at Nagoya University has finally explained the mysterious structural changes of this phase transition and its related electronic behavior.
"Researchers have questioned that the TMTTF (tetramethyltetrathiafulvalene) salt shows a charge disproportionation transition at 67 Kelvin but no relevant changes in its crystal structure. This transition is a long-standing mystery known as a 'structure-less transition'," explains lead author Shunsuke Kitou.
TMTTF is an organic donor that is also found in some organic superconductors. Just above the temperature that liquid nitrogen freezes, this organic crystal behaves as an insulator. But as the temperature is lowered it goes through electronic and magnetic changes.
Until now these structural changes were too small to measure directly. Using the X-ray source at SPring8, in Hyogo Japan, the team could precisely determine the crystal structure at each stage. The structure-less transition involves the formation of a two-dimensional Wigner crystal, based on a change in the distribution pattern of electrons in the structure.
"We have precisely characterized the subtle structural changes across this transition and finally provided a complete physical explanation for the apparent unchanging structure of this organic conductor," says group leader Hiroshi Sawa. "Accurate crystallographic data is still lacking for many organic conductors and we hope our findings will inspire other groups to look more closely at these systems. A better understanding of their complex behavior could pave the way to a range of new functional electronic materials."
The article, "Successive Dimensional Transition in (TMTTF)2PF6 Revealed by Synchrotron X-ray Diffraction," was published in Physical Review Letters. https:/
Koomi Sung | EurekAlert!
Custom sequences for polymers using visible light
22.03.2018 | Tokyo Metropolitan University
The search for dark matter widens
21.03.2018 | American Institute of Physics
An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.
The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...
In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.
Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...
Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.
They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...
A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...
For the first time, an interdisciplinary team from the University of Basel has succeeded in integrating artificial organelles into the cells of live zebrafish embryos. This innovative approach using artificial organelles as cellular implants offers new potential in treating a range of diseases, as the authors report in an article published in Nature Communications.
In the cells of higher organisms, organelles such as the nucleus or mitochondria perform a range of complex functions necessary for life. In the networks of...
19.03.2018 | Event News
16.03.2018 | Event News
13.03.2018 | Event News
22.03.2018 | Trade Fair News
22.03.2018 | Earth Sciences
22.03.2018 | Earth Sciences