V Laboratory
Department of Physics
Nagoya University
Furocho, Chikusa, Nagoya

Competition between charge order and dimer Mott insulator in β-(meso-DMBEDT-TTF)2PF6

Internal degrees of freedom are a central idea penetrating into various fields in physics. Organic molecular conductors possess unique internal degrees of freedom such as molecular arrangement or change degrees of freedom in the molecular and/or multimer, leading to various interesting electronic and magnetic phases. In this study, we have performed an infrared imaging spectroscopy on the dimer-type molecular salt β-(meso-DMBEDT-TTF)2PF6 at BL43IR, SPring-8, and found a spatially-inhomogeneous state consisting of dimer Mott insulator and charge order at low temperatures. This result indicates that these two correlated insulating states are almost degenerate and this compound is actually located near the phase boundary of these phases, offering a new understanding for the complex phase diagram of molecular solids.

This work was done in collaboration with Dr. Ikemoto, Dr. Moriwaki (JASRI), Prof. Mori’s group (ISSP, Tokyo), and Prof. Sasaki’s group (IMR, Tohoku).

"Optical Conductivity Measurement of a Dimer Mott-Insulator to Charge-Order Phase Transition in a Two-Dimensional Quarter-Filled Organic Salt Compound"
by Ryuji Okazaki, Yuka Ikemoto, Taro Moriwaki, Takahisa Shikama, Kazuyuki Takahashi, Hatsumi Mori, Hideki Nakaya, Takahiko Sasaki, Yukio Yasui, Ichiro Terasaki
Phys. Rev. Lett. 111, 217801 (2013).

(Figure) Charge order and dimer Mott insulator in β-(meso-DMBEDT-TTF)2PF6.