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2016.04.05 Annual Report 2
2016.03.15 Conference Presentation Practice
2016.03.08 K. Ueda
2016.03.01 Annual Report 1
2016.02.23 Literature Survey Report
2016.02.16 "Cooperative Interactions between Valence Bond Formation and Inter-Site Coulomb Repulsions Specific to an Interchange of Energy Levels in the Molecular Orbitals" Dr. T. Yamamoto（Ehime University, Associate Professor）
X[M(dmit)2]2 salts [M=Pt and Pd] exhibit the interchange of energy levels in the molecular orbitals (HOMO-LUMO inversion) owing to the tight dimerization. Nevertheless, the intrinsic role of the HOMO-LUMO inversion in the charge and spin distributions has not been studied. The accumulation of the recent experimental results revealed that the valence bond ordering and the inter-site Coulomb repulsions all cooperate in this HOMO-LUMO inversion system. Interestingly, the charge and spin distribution due to the cooperative interaction between neighboring dimers is different from that within a dimer. Interestingly, the competition between these cooperative interactions is observed in several X[M(dmit)2]2 salts. This result indicates a novel degree of freedom arising from the HOMO-LUMO inversion in the present systems. The magnitudes of the intra-dimer and inter-dimer cooperative interactions are evaluated using the frequencies of the C=C stretching modes exhibiting the electron-molecular vibrational (e-mv) interaction. The ground states of X[Pd(dmit)2]2, including the anti-ferromagnetic state, is mapped using the magnitudes of cooperative interactions defined above. From the viewpoints of these cooperative interactions, I will discuss the puzzling phenomenon that the 2D layer of the spin-liquid system, β'-Et2Me2Sb[Pd(dmit)2]2, deviates from the ideal triangular lattice whereas the 2D layers of the non-magnetic insulators, β'-Et2Me2Sb[Pd(dmit)2]2 and monoclinic-EtMe3P[Pd(dmit)2]2, are close to the ideal triangular lattice.
2016.02.09 Literature Survey Report
2016.01.26 Dr. Seki (Computational Condensed Matter Physics Laboratory, RIKEN)
2016.01.19 Midterm Report 2
2016.01.12 Midterm Report 2
2015.12.15 Midterm Report 1
2015.12.08 Abdel Jawad Majed
2015.12.01 Literature Survey Report
2015.11.24 Literature Survey Report
2015.11.19 "Low-Frequency Charge Carrier Dynamics in Quasi-2D Molecular Conductors" Prof. Jens Muller (Institute of Physics, Goethe-University Frankfurt, Germany)
Electronic noise, on the one hand, is mostly considered an unwanted nuisance and is sought to be reduced or even eliminated, since it ultimately limits the accuracy of physical measurements. On the other hand, understanding the microscopic origin of the different noise sources may help to improve the signal-to-noise ratio of measurements on semiconductors and therefore the performance of semiconductor sensors and devices.
Another point of view, however, is to consider “noise as the signal”, since the frequency-dependent fluctuations are related to the autocorrelation function of the measured quantity. Therefore, fluctuation spectroscopy is a powerful tool for studying the microscopic kinetics of charge carriers in condensed-matter systems.
In this talk, we will discuss how resistance fluctuations, in particular 1/f- and random-telegraph noise, reveal otherwise ‘hidden’ pieces of information on the low-frequency dynamics of quasi-2D organic charge-transfer salts (ET)2X. We will focus on (i) the structural, glass-like ordering of the ET molecules’ terminal ethylene groups and the possibility to predict the occurrence of such a glass transition for different crystal structures, and (ii) the critical slowing down of the fluctuations at the Mott metal-insulator transition.
In an outlook, we will mention new results on insulating materials exhibiting ferroelectric ordering or relaxor-type behavior.
2015.11.10 "Atomic Layer Deposition in Solution" Y. Sato
Rapid progress of nanoscience and nanotechnology pushes the device requirements toward more complex three-dimensional nanostructures and even more sophisticated functionalities. Atomic-layer-deposition (ALD), a layer-by-layer growth technique of thin film based on ‘self-limiting’ surface chemistry, is a powerful method to meet such demands because it provides atomic-scale precision of layer thickness and composition, and, importantly, is applicable to even non-planer substrates. Nevertheless, ALD has a major limitation that it needs volatile and thermally robust precursors since the deposition process is done basically in gas phase.
In this seminar, I will introduce a newly-reported ‘solution ALD’ technique, which realizes precisely controlled oxide layer growth from various kinds of precursors under milder reaction condition, without much sacrificing the merit of gas-phase ALD. .Some other solution-based layer-by-layer growth methods will be also briefly reviewed.
2015.10.27 Mr. K. Shimada（Department of Physics, Faculty of Science, Toho University D3）
2015.10.20 Dr. T. Kawakami（Quantum Chemistry Lab., Department of Chemistry, Osaka University Graduate School of Science Assistant Professor）
2015.10.13 Literature Survey Report
2015.10.06 Literature Survey Report
2015.09.29 Midterm Report 2
2015.09.15 Conference Presentation Practice
2015.08.25 Midterm Report 1
2015.07.21 "Electronic Transport of Low Dimensional Hybrid Nanomaterials: Colloidal Quantum Dot Assemblies and Polymer-wrapped Carbon Nanotubes" Dr. Satria Zulkarnaen Bisri (RIKEN CEMS:Emergent Device Research Team）
The exploitation of quantum-size-effect in solution-processable nanomaterials is prospective for broad range applications, including energy-harvesting- and low-energy-consumption devices that will contribute to the future sustainable development of our society. Nevertheless, many of physical properties of these materials associated with the charge transport are still not well understood in particular when translating them into solid-state assemblies. Many challenges related with the charge transport still hampering their use for high-end and high-speed applications. I will present experimental studies on the field-effect control of charge carrier transport in colloidal quantum dot assemblies (0D) and polymer-wrapped carbon nanotubes networks (1D). Through fine tuning of field-induced carrier doping utilizing field-effect transistors, ambipolar transport - coexisting of holes and electron current - are demonstrated in these materials with high mobility values. This ambipolar transport provides opportunity to investigate the dynamics of both holes and electrons in the materials system with different conditions such as very high carrier density, high electric field, as well as high current density operation. Applications of these solution-processable nanomaterials as well as both ambipolar transistor and electric-double-layer transistor techniques are promising to become rich playground for novel (opto)electronic properties and emerging sources of new device functionalities such as flexible exa-scale computing, photovoltaic and thermoelectric devices.
2015.07.14 "磁性と誘電・伝導性が相関した物質におけるマルチプローブ研究" Dr. T. Honda (KEK)
2015.07.07 Literature Survey Report
2015.06.30 Literature Survey Report
2015.06.23 Midterm Report
2015.06.16 Midterm Report
2015.06.02 "Electron Transfer through Weak-Hydrogen Bonds" K. Ueda
Recently, some relatively strong interactions between C-H…O and C-H…pi have been noted, and the hydrogen-bond concept was expanded to such interactions as weak hydrogen-bond. These strengths are weaker than O-H…O and N-H…O type hydrogen bonds; however, the role of these are important in condensed matters (of course molecular conductors) because weak hydrogen-bonds are coexistent in many directions between non-special function groups. In this seminar, I will introduce the perturbation effect of such weak hydrogen bonds for molecular orbitals of proton acceptor and proton donor: for example charge transfer and MO hybridize.
2015.05.26 "π-d系有機導体λ-(BETS)2FeCl4における特異な磁気構造が磁気トルクにもたらす影響" Ms. Sugiura (Tsukuba Univ.)
2015.05.12 Literature Survey Report
2015.04.28 Literature Survey Report
2015.04.21 "Mott Transition in EtMe3P[Pd(dmit)2]2" Abdel Jawad Majed
Studies of the metal-insulator transition of the Mott type is of great interest to the condensed matter community as anomalous superconducting states are often found in proximity to such a transition. In this talk, I will summarize the current experiential results related to the Mott transition and present the pressure and temperature dependence of the Hall coefficient in EtMe3P[Pd(dmit)2]2. Surprisingly the Hall coefficient is found to be temperature and pressure independent in the metallic state of EtMe3P[Pd(dmit)2]2, implying that the carrier number and the density of state does not change on the metal side of the Mott transition.
2015.04.14 "Dirac Cone Formation in Single-Component Molecular Conductors" R. Kato
Single-component molecular conductors belong to a multi-band system where both HOMO and LUMO bands contribute to the formation of conduction bands. In most single-component molecular crystals, these two bands are separated from each other at ambient pressure, which leads to insulating properties. Application of high pressure can expand the band width for both bands and their overlap induces the conducting behavior including metallization and superconductivity. In the process of resistivity measurements and the first principles DFT calculations for single-component molecular crystals under high pressure, we noticed a possibility that the Dirac cones are formed in a crystal of dithiolene complex [Pd(dddt)2]. The Dirac cone formation in [Pd(dddt)2] can be understood by a simplified two-dimensional tight-binding model where the HOMO band is convex upward and the LUMO band is convex downward. An overlap of these two bands provides a closed intersection at the Fermi level (Fermi line) in the k-space, if there is no HOMO-LUMO interaction.
An introduction of the HOMO-LUMO interactions removes the degeneracy on the Fermi line and results in a gap formation. However, if there is a line on which the HOMO-LUMO interaction is zero, the two bands contact at the points where the line intersects with the Fermi line, leading to the formation of the Dirac cones.
In the first part of my seminar, I will introduce two pragrams (Fe2d and Bcalc) for the tight-binding band calculations.
2015.04.07 Annual Plan
