Charge disproportionation, everywhere!

T. Takahashi; K. Hiraki; S. Moroto; N. Tajima; Y. Takano; Y. Kubo; H. Satsukawa; R. Chiba; H.M. Yamamoto; R. Kato; T. Naito

doi:doi:10.1051/jp4:2005131002

Numéro		J. Phys. IV France Volume 131, December 2005


Page(s)		3 - 8
DOI		https://doi.org/10.1051/jp4:2005131002
Publié en ligne		18 janvier 2006

International Workshop on Electronic Crystals
S. Brazovskii, P. Monceau and N. Kirova
J. Phys. IV France 131 (2005) 3-8
DOI: 10.1051/jp4:2005131002

Charge disproportionation, everywhere!

T. Takahashi¹, K. Hiraki¹, S. Moroto¹, N. Tajima², Y. Takano¹, Y. Kubo¹, H. Satsukawa¹, R. Chiba¹, H.M. Yamamoto², R. Kato² and T. Naito³

¹ Department of Physics, Gakushuin University, Tokyo 171-8588, Japan
² RIKEN, The Institute of Physical and Chemical Research (RIKEN), JST-CREST, Saitama 351-0198, Japan
³ Creative Research Initiative "Sosei" Hokkaido University, Hokkaido 001-0020, Japan

Abstract
Charge disproportionation (CD) recently observed in many organic conductors is reviewed. CD is closely related to the charge ordering (CO) but is observed even when no long range CO is established. In a $\theta$ -phase BEDT-TTF salt, (BEDT-TTF)₂RbZn(SCN)₄, an extremely slow dynamics of CD has been observed above $T_{\rm MI}$ . A similar phenomenon is also observed in the Cs-analog, (BEDT-TTF)₂CsZn(SCN)₄. However, a spin-singlet ground state without CD is suggested in this salt at low temperatures. It is shown that $\alpha$ -(BETS)₂I₃ exhibits CD at low temperatures, as in $\alpha$ -(BET-TTF)₂I₃. Recently, an abnormal line broadening has been observed in ¹³C-NMR of (TMTSF)₂FSO₃ under pressure as well as in ⁷⁷Se-NMR of $\lambda$ -(BETS)₂FeCl₄ in a high field. We expect that both are very likely caused by a large CD among the organic molecular sites.