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!
Atomic structure of ultrasound material not what anyone expected
21.02.2018 | North Carolina State University
Hidden talents: Converting heat into electricity with pencil and paper
20.02.2018 | Helmholtz-Zentrum Berlin für Materialien und Energie
Quantum computers may one day solve algorithmic problems which even the biggest supercomputers today can’t manage. But how do you test a quantum computer to...
For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.
In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...
Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale
Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...
For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.
But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...
Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.
The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...
15.02.2018 | Event News
13.02.2018 | Event News
12.02.2018 | Event News
22.02.2018 | Life Sciences
22.02.2018 | Physics and Astronomy
22.02.2018 | Earth Sciences