Sulfur K-edge X-ray absorption spectra for BETS and BEDT-TTF charge transfer salts: a novel probe for the determination of hole concentration

Charge ordering inθ−(BEDT−TTF)2

“…As shown by the asterisks in Fig. 4͑b͒, the two carbon atoms in the central CvC bond are replaced by 13 C atoms in the isotope-substituted sample. Because only the two gerade modes 2 and 3 include the central CvC bond stretching, these modes can be distinguished from the ungerade mode 27 by the isotopeshift measurement.…”

“…Nakamura et al discovered a sign of CD in the angular dependence of the electron-spin-resonance spectrum of -(ET) 2 CsZn(SCN) 4 , which stimulated an interest in the CD phenomenon of the -type ET salts. 6 Miyagawa et al 7 and Chiba et al 8 performed the 13 C-nuclear-magnetic-resonance measurements for -(ET) 2 RbZn(SCN) 4 , and reported the existence of chargerich and -poor sites in the insulating phase. Meanwhile, Seo and Fukuyama have carried out a mean-field calculation to understand the mechanism of the charge localization 9, 10 and have proposed that a stripe-patterned charge ordering is stabilized in the insulating phase owing to intermolecular Coulomb repulsive forces.…”

“…Recently, Mori et al have proposed that the intermolecular Coulomb interaction can be estimated from the electrostatic energies between the point charges on a molecule calculated by the extended Hückel method. 11 Among various approaches applicable to the research of the charge ordering, 12,13 vibrational spectroscopy can be one of the powerful methods 14 for the following reasons. First, the frequencies of the CvC stretching modes of ET sensitively shift depending on the charge population upon the molecule.…”

Spectroscopic Studies of the Phase Transition from the Mott Insulator State to the Charge-Ordering State of κ-(ET)4[M(CN)6][N(C2H5)4]·2H2O (M = CoIII and FeIII) Salts

“…The spectroscopy methods, especially within the infrared region, are very useful for investigations of crystalline organic conductors, providing information about the electronic structure and electron–electron and electron–phonon interactions . Among various methods applicable to the research of the charge ordering, , the vibrational spectroscopy is one of the most powerful methods . The charge disproportionation (CD) ratio can be easily estimated since the frequencies of the CC stretching modes of ET sensitively shift depending on the charge density on the molecule.…”

Vibrational and Electronic Structure, Electron-Electron and Electron-Phonon Interactions in Organic Conductors Investigated by Optical Spectroscopy

“…The special attention will be paid to the description of the electronic structure and determination of transport parameters. It will be shown that the most powerful method to investigate the charge ordering phenomena is the vibrational spectroscopy [32][33][34]. The results presented in this chapter were obtained by the spectroscopic methods including IR, Raman and UV-Vis.…”