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ISCOM2009

announcement. International symposium on crystalline organic metals, superconductors, ferromagnets. ISCOM2009. At Niseko in Hokkaido, Japan. On Sep. 12 – 17, 2009 (Sep. 12; get-together). ECRYS2008 , Cargese, Corsica, Aug. 25-30, 2008.

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ISCOM2009

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  1. announcement International symposium on crystalline organic metals, superconductors, ferromagnets ISCOM2009 At Niseko in Hokkaido, Japan On Sep. 12 – 17, 2009 (Sep. 12; get-together)

  2. ECRYS2008 , Cargese, Corsica, Aug. 25-30, 2008 New Aspects of Neutral-Ionic Transition (NIT)Revealed by Magnetic Resonance K. Kanoda, Applied Physics, University of Tokyo Collaborators F. Iwase ( present; IMS), K. Miyagawa Y. Tokura, H. Okamoto S. Horiuchi K. Murata Univ. Tokyo AIST Osaka City Univ. Outline 0. Introduction to NIT 1. Observation of quantum critical fluctuations in NIT 2. Separation of charge transfer and dimerization

  3. Neutral-Ionic transition (NIT) TTF-QCl4 TTF Torrance et al., PRL. (1981) QCl4 Neutral paraelectric Charge transfer -- Redox Temperature Pressure Dimerization --symmetry breaking Ionic ferroelectric Spin-Peierls Charge-lattice-coupled phenomena

  4. NIT phase diagram Lemee-Cailleau et al. PRL 79, 1690 (1997) TTF-QCl4 Neutral phase Ionic phase Okamoto et al. 1st-order transition of simultaneous CT and dimerization

  5. by Horiuchi, Tokura NIT in DMTTF-QCl4 –continuous and quantum Chemical pressure DMTTF QCl4 Physical pressure Neutral Ionic Continuous transition Horiuchi et al., J. Am. Chem. Soc., 123, 665 (2001).

  6. - - e e nQ nQ Nuclear quadrupole resonance (NQR) probes the charge state and symmetry of the lattice I=3/2 rf pulse nucleus Electric field gradient (EFG) Resonance frequency Charge transfer line splitting line shift Dimerization Cl or Br nuclei Cl or Br nuclei

  7. TTF-QCl4 Cl-NQR J. Gallier et al., Phys. Rev. B, 47, 11688 (1993). Charge transfer Spectral shift NQR Spectral splitting Symmetry breaking (dimerization) Iwase et al., JPSJ (2007) Neutral Ionic Ionic QCl4 Neutral

  8. NQR spectra

  9. Spin-lattice relaxation rate 1/T1 DMTTF-QCl4 35Cl NQR DMTTF-QBr4 Br NQR Barrett formula: T0：Curie-Weiss temperature T1：characteristic crossover temperature dividing the quantum and classical region

  10. Pressure-induced NIT at low T NQR spectra at 5K dimerization Pc(20K)=1.41 kbar 20 K b=0.55 Pc(5K)=1.32 kbar 5 K b=0.55 mean-field behavior R. Morf et al., PRB 16462 (1977).

  11. Pressure-induced NIT; continuous and quantum 1/T1~(Pc-P)-1 1/T1~(Pc-P)-2.3 T1~(Pc-P)2.3 0.22 79Br NQR Spins are hidden all the way across the transition DMTTF-QBr4 5 K QBr4 molecule Quantum critical fluctuations

  12. Extended phase diagram of TTF-QCl4 Charged spin soliton Short-range order Dimer liquid Dimer crystal polarization Long-range order

  13. Two messages on NIT • Critical fluctuations of N-I transition at low temperatures. They are likely quantum. • Charge-lattice separation in low-energy scale in a wide P-T range.

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