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2009.2.19 "Diamagnetic CpCo(dithiolene) and Paramagnetic CpNi(dithiolene) Complexes" 野村 光城
Metal dithiolene complexes are classified into three main categories as follows: (1) homoleptic dithiolene complexes, (2) heteroleptic dithiolene complexes, and (3) organometallic dithiolene complexes. I will be talking about the organometallic [CpM(dithiolene)] (M = Co and Ni) complexes and those new synthetic procedure, chemical reactivities, structures and magnetic properties. A characteristics of the [CpCo(dithiolene)] complexes is coexistence of aromaticity and unsaturation. The paramagnetic [CpNi(dithiolene)] (S = 1/2) families have some intermolecular weak bondings at solid state but show strong magnetic interactions through S・・・S uniform chain, dithiolene・・・dithiolene dimer, Cp・・・dithiolene zigzag chain and Cp・・・Cp dimer.
2009.2.12 "Study of conductivity and magnetism in molecular materials" 大島 勇吾
I will talk about my interests in molecular materials.Latest studies of molecular conductors and nano-scaled molecular magnets will be presented.My talk consists of four topics.
i) Cyclotron resonance on molecular conductors
ii) Submillimeter-wave Electron Spin Resonance (ESR) on pi-d system
iii) Study of nanometer-sized molecular magnets
iv) Magnetotransport properties of single-walled carbon nanotube
2009.1.22 "Photo-Induced Phase Transition by Coherent Vibrational Excitation" 田久保 直子
I will talk about a new type of photo-induced phase transition, which is caused by coherent vibrational excitation. An ultrafast electronic phase transition, associated with melting charge- and orbital-order, is driven by selectively exciting the Mn-O stretching mode with THz wave in perovskite manganite, Pr0.7Ca0.3MnO3 and La0.5Sr1.5MnO4.
2009.1.15 "NMR studies on molecular conductor, magnets and superconductors" 開 康一／学習院大学理学部物理学科
Elctronic states on the molecular based correlated systems investigated by Nuclear Magnetic Resonance (NMR) technique will be discussed. especially, microscopic evidence of the Jaccarino-Peter compensation mechanism on the magnetic field induced superconductor (lambda(BETS)2FeCl4), charge oder/disproportionation on zero/narrow gap system (alpha(ET)2I3 and its analogues), magnetic ordering states on frustrated spin system (beta'Et2Me2P[Pd(dmit)2]2) will be discussed.
2008.12.25 "Giant dielectric response in the one-dimensional charge-ordered semiconductor (NbSe4)3I" Mohamad M. Ahmad
Increasing number of dielectric measurements of charge-ordered inorganic and organic systems is reported. Giant dielectric response has already been observed in one-dimensional(TMTTF)_2 X and (DI-DCNQI)_2 Ag systems and in the insulating two-leg ladder Sr_14 Cu_24 O_41 material. In this seminar, I will show the results of the broadband dielectric spectroscopy of the one dimensional charge ordered (NbSe4)3I,where intrinsic giant dielectric constant was detected in the charge ordered state.
2008.12.18 "Theory for inter-layer magnetoresistance in α-(BEDT-TTF)2I3" 森成 隆夫／京都大学基礎物理学研究所
Since the discovery of half-integer quantum Hall effect in graphene, which is the single-layered graphite, massless Dirac fermions in condensed matter systems have received much attention. In contrast to graphene, which is a purely two-dimensional system, the organic conductor α-(BEDT-TTF)2I3 is the first bulk material where the massless Dirac fermion-like spectrum is realized. Furthermore electronic correlations, which lead to charge ordering and superconductivity in this system, can be controlled by pressure. From band calculations and first principle calculations, it is suggested that the Dirac cone in α-(BEDT-TTF)2I3 is tilted and anisotropic. However, these features have never been verified experimentally. In this talk,I will show that the parameters characterizing Dirac cone are determined from the interlayer magnetoresistance. Using the analytic Landau level wave functions and assuming local tunneling of electrons, theoretical formula for the interlayer magnetoresistance is derived. It is shown that the resistivity as a function of the azimuthal angle of the magnetic field takes the maximum in the direction of the tilt.
2008.11.6 "RIKEN/CNRS International Collaboration Unit" Patrick Batail and "Dynamic Halogen- and Hydrogen-bonded Spacers, Active Components in Molecular Conductors" Cyprien Lemouchi
2008.10.16 「平成20年度 中間報告(1)」 田嶋 尚也、福永 武男
2008.10.9 "Photo-induced effect in oxide thin films" 田久保 直子
I will talk about my research background. Specifically, I will review my recent studies, "Photo-induced phase transition in manganite thin films" and "Photo-induced effect in tin dioxide thin films".
2008.9.18 "Synthesis and studies of Ni(dmit)2-based complexes" Guillaume Darpin
I will present you my work and the different results I obtained during this internship.
2008.9.4 "Impedance (dielectric) spectroscopy of some fluoride ion conductors and other ceramic materials" Mohamad M. Ahmad
Impedance spectroscopy measurements have been performed for Pb1-xSnxF2 solid solutions over wide ranges of frequencies and temperatures.
The impedance data has been analyzed in the conductivity formalism, where the hoping rates and the concentration of mobile ions could be estimated. Some of these solid solutions with nanosized grains, in the range of 26 nm, exhibit giant values of the dielectric constant, a behavior which is opposite to what is usually observed for giant dielectric oxide materials.
Moreover, the effect of aging on the dielectric properties of BaTiO3 ceramics is briefly discussed.
2008.6.19 "Charged impurity scattering in graphene" 川椙 義高
A single layer of graphite, graphene has been intensively investigated as Dirac fermion system. The gate voltage dependence of the conductivity reflects the energy dispersion. However, it is controversial whether the transport properties are intrinsic or governed by impurities. I introduce a potassium doping effect which clarifies the charged impurity effect.
2008.6.5 "Hall effect in Mott insulator" 田嶋 尚也
I will talk about the Hall effect in Mott insulator. Many superconductivities are realized next to the Mott insulatore phase. In order to understand those superconductivities, it is essential to study the carrier system in the Mott insulating state. The Hall effect is a useful tool to investigate the primitive properties of carriers.
2008.5.29 "Electrochromic materials based on metal coordination polymers" 久保 和也
Electrochromic materials have received great interest as molecular switches for optical and electronic applications. Commercial applications include a large amount of areas, such as anti-glare mirrors and glasses, indicators and labels, smart windows, and information storage. Most applications require electrochromic materials with high contrast ratio, good coloration efficiency, lonjg-term stability, and write-erase efficiency. Most frequently investigated components for these purposes are conducting polymers, molecular dyes, and metal oxides. In this seminar, I will show you the latest report about the electrochromic materials based on the metal coordination polymers from Journal of the American Chemical Society.
2008.5.22 "Polyfuran, conducting polymer" Guillaume Darpin
Furan is one of the heteroaromatic ring compounds and has been extensively studied. But this compound has attracted less attention than pyrrole, thiophene and aniline as a monomer in this context because of its high oxidation potential. However many works have been carried out to overcome this difficulty by changing the experimental conditions. In this seminar, I'll describe the methods of synthesis and results in terms of conductivity, structure and morphology.
2008.5.15 "分子性導体におけるゼロギャップ状態" 小林晃人博士
The apparent zerogap fermions in α-(BEDT-TTF)2I3 have recently been proposed to obey the tilted Weyl equation. The Hall conductivity, the conductivity and the orbital susceptibility have been investigated theoretically. It has been proposed that the sharp but continuous reversal of the sign of the Hall coefficient is possible at low temperatures if the extremely small amount of electron doping (about 1ppm) exists. These results can explain very anomalous features of Hall coefficient observed by N. Tajima (2007). In addition, it is shown that the orbital diamagnetism can have a peak at the temperatures where the Hall coefficient changes sign. All these strong temperature dependences of both the Hall coefficient and the orbital diamagnetism are due to the inter-band effects of magnetic field. Effects of Coulomb interactions among electrons in the presence of magnetic field will also be studied.
2008.5.8 "Shape of dendrites -An electrochemical case-" 山本 浩史
Dendrite is a very common feature in snowflakes, dielectric breakdown (or thunder), bio-mineralization and so on. Ramified metallic electrodeposits formed by electrochemical processes also show dendric shapes. Since the experimental parameters can be finely tuned for this kind of dendrites, the comparison between theory and experiment has been deeply discussed on these electrodeposits.
In this seminar, I'll describe the theories and experiments of electrodeposits in two-dimension in historical order. These information might be useful in our daily electrochemical crystal growth.
2008.5.1 literature survey
2008.4.24 "Clamp-type pressure cells for single crystal X-ray diffraction" 福永 武男
There are many examples of the organic conductors whose insulating states are changed to superconductor (metal, semiconductor) states under hydrostatic pressure. Therefore, it is important to investigate the crystal structures under the pressure, in order to understand the electronic states of those organic conductors. Recently, clamp-type pressure cells have been designed for crystal structure determination.
In this seminar, I'll talk about the merit of the clamp-type pressure cells, and compare them with diamond anvil cells.