14,987 research outputs found
Magnetism and Superconductivity in a Two-band Hubbard Model in Infinite Dimensions
We study a two-band Hubbard model using the dynamical mean-field theory
combined with the exact diagonalization method. At the electron density ,
a transition from a band-insulator to a correlated semimetal occurs when the
on-site Coulomb interaction is varied for a fixed value of the
charge-transfer energy . At low temperature, the correlated semimetal
shows ferromagnetism or superconductivity. With increasing doping , the
ferromagnetic transition temperature rapidly decreases and finally becomes zero
at a critical value of . The second-order phase transition occurs at high
temperature, while a phase separation of ferromagnetic and paramagnetic states
takes place at low temperature. The superconducting transition temperature
gradually decreases and finally becomes zero near () where the
system is Mott insulator which shows antiferromagnetism at low temperature.Comment: 3 pages, 5 figures, proceedings of the International Conference on
Strongly Correlated Electrons with Orbital Degrees of Freedom (ORBITAL2001
Functional organic materials for electronics industries
Topics closely related with organic, high molecular weight material synthesis are discussed. These are related to applications such as display, recording, sensors, semiconductors, and I.C. correlation. New materials are also discussed. General principles of individual application are not included. Materials discussed include color, electrochromic, thermal recording, organic photoconductors for electrophotography, and photochromic materials
First-Principles Study on Electron-Conduction Properties of C Chains
The electron-conduction properties of fullerene chains are examined by
first-principles calculations based on the density functional theory. The
conductivity of the C dimer is low owing to the constraint of the
junction of the molecules on electron conduction, whereas the C monomer
exhibits a conductance of 1 G. One of the three degenerate
states of C is relevant to conduction and the contributions of the
others are small. In addition, we found a more interesting result that the
conductance of the fullerene chain is drastically increased by encapsuling
metal atoms into cages.Comment: 10pages and 5 figure
New structural model for GeO2/Ge interface: A first-principles study
First-principles modeling of a GeO2/Ge(001) interface reveals that sixfold
GeO2, which is derived from cristobalite and is different from rutile,
dramatically reduces the lattice mismatch at the interface and is much more
stable than the conventional fourfold interface. Since the grain boundary
between fourfold and sixfold GeO2 is unstable, the sixfold GeO2 forms a large
grain at the interface. On the contrary, a comparative study with SiO2
demonstrates that SiO2 maintains a fourfold structure. The sixfold GeO2/Ge
interface is shown to be a consequence of the ground-state phase of GeO2. In
addition, the electronic structure calculation reveals that sixfold GeO2 at the
interface shifts the valence band maximum far from the interface toward the
conduction band.Comment: 18 pages, 5 figures, and 2 table
A critical examination of discrete lattice and dispersed barrier hardening
Critical assessment of discrete lattice and dispersed barrier hardening theories of thermally activated deformation of metal
Fabrication of graphene nanoribbon by local anodic oxidation lithography using atomic force microscope
We conducted local anodic oxidation (LAO) lithography in single-layer,
bilayer, and multilayer graphene using tapping-mode atomic force microscope.
The width of insulating oxidized area depends systematically on the number of
graphene layers. An 800-nm-wide bar-shaped device fabricated in single-layer
graphene exhibits the half-integer quantum Hall effect. We also fabricated a
55-nm-wide graphene nanoribbon (GNR). The conductance of the GNR at the charge
neutrality point was suppressed at low temperature, which suggests the opening
of an energy gap due to lateral confinement of charge carriers. These results
show that LAO lithography is an effective technique for the fabrication of
graphene nanodevices.Comment: 4 pages, 4 figure
On the p-adic geometry of traces of singular moduli
The aim of this article is to show that p-adic geometry of modular curves is
useful in the study of p-adic properties of traces of singular moduli. In order
to do so, we partly answer a question by Ono. As our goal is just to illustrate
how p-adic geometry can be used in this context, we focus on a relatively
simple case, in the hope that others will try to obtain the strongest and most
general results. For example, for p=2, a result stronger than Thm.1 is proved
in [Boylan], and a result on some modular curves of genus zero can be found in
[Osburn] . It should be easy to apply our method, because of its local nature,
to modular curves of arbitrary level, as well as to Shimura curves.Comment: 3 pages, Late
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