SPring-8, the large synchrotron radiation facility

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New Phase Transition Phenomenon in an Organic Molecular Conductor A Novel Route for an Organic Electronics (Press Release)

Release Date
18 Nov, 2013
  • BL43IR (Infrared Materials Science)

Department of Physics, Nagoya University
Japan Synchrotron Radiation Research Institute (JASRI)
Institute for Solid State Physics (ISSP), The University of Tokyo
Institute for Materials Research (IMR), Tohoku University

The state of matter dramatically varies with external temperature. For example, water (liquid phase) changes into ice (solid phase) with cooling. Such a phase change is known as the phase transition. Here, water and ice coexist only at 0 degrees centigrade. At the higher temperatures, the liquid phase is realized. On the other hand, at the lower temperatures, the solid phase emerges. The temperature of 0 degrees centigrade is thus the boundary between liquid and solid phases, known as the phase transition temperature.

The research group of Nagoya University (Assist. Prof. Ryuji Okazaki and Prof. Ichiro Terasaki in the laboratory of condensed matter physics of functional materials), in collaborations with Dr. Yuka Ikemoto and Dr. Taro Moriwaki in JASRI, Prof. Mori’s group in The University of Tokyo, and Prof. Sasaki’s group in Tohoku University, has performed an infrared imaging experiment in BL43IR, SPring-8(*1), and has found that two different electronic states spatially coexist in an organic molecular conductor in a broad temperature range from the phase transition temperature of -200 degrees centigrade nearly to the absolute zero temperature. This is highly anomalous behavior because a spatially-homogeneous state is usually realized below the phase transition temperature. Such an inhomogeneous state can be sensitively changed by the external field, such as electric field, leading to a possible organic nonlinear device(*2) using the inhomogeneous state.

This research result was published in Physical Review Letters (online published date: 18 Nov. 2013).

This work was supported by a Grant-in-Aid for Scientific Research (B) (No. 21340106), by a Grant-in-Aid for Young Scientists (B) (No. 23740266), and by a Grant-in-Aid for Scientific Research on Innovative Areas “Molecular Degrees of Freedom” and “Heavy Electrons”.

Title:"Optical Conductivity Measurement of a Dimer Mott-Insulator to Charge-Order Phase Transition in a Two-Dimensional Quarter-Filled Organic Salt Compound"
Authors: Ryuji Okazaki(1), Yuka Ikemoto(2), Taro Moriwaki(2), Takahisa Shikama(3), Kazuyuki Takahashi(3,4), Hatsumi Mori(3), Hideki Nakaya(5), Takahiko Sasaki(5), Yukio Yasui(1,6), Ichiro Terasaki(1)
Affiliations: (1) Department of Physics, Nagoya University, (2) Japan Synchrotron Radiation Research Institute (JASRI), (3) Institute for Solid State Physics (ISSP), The University of Tokyo, (4) Department of Chemistry, Kobe University, (5) Institute for Materials Research (IMR), Tohoku University, (6) Department of Physics, Meiji University
Physical Review Letters 111 217801, published 18 November 2013


Figure 1
Figure 1

Photograph of the organic compound β-(meso-DMBEDT-TTF)2PF6 with a needle-like shape.

Figure 2
Figure 2

Schematic figure of coexisting two different electronic states in the organic compound. Using the infrared imaging spectroscopy in BL43IR, SPring-8, the electron distribution is found to be different in left and right sides of the crystal. The left side is a dimer Mott-insulator phase, in which the electron locates on the dimer. The right side is a checkerboard-type charge order phase.

*1 SPring-8

A large synchrotron radiation facility that generates the highest-quality synchrotron radiation, located in Hyogo prefecture, Japan. Owned by Riken, and operated by JASRI. The nickname SPring-8 is short for Super Photon ring-8 GeV. Synchrotron radiation refers to the strong and highly oriented electron magnetic waves generated when the orbit of electrons, accelerated to a near-light speed, is bent by magnetic field. Applications of the synchrotron radiation produced by SPring-8 includes nanotechnology, biotechnology and industrial use.

*2 Nonlinear device
Electronics that exhibits nonlinear conduction phenomena, such as diodes and transistors. In usual resistors, the flowing electrical current is proportional to the applied electric field, known as the Ohm’s law. On the other hand, in nonlinear devices, the field and the current possess a nonlinear relation, and the resistance of device largely changes with electric field.

For more information, please contact:
  Assistant Prof. Ryuji Okazaki (Department of Physics, Nagoya University)
    E-mail : mail1

  Prof. Ichiro Terasaki (Department of Physics, Nagoya University)
    E-mail : mail2

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