16,402 research outputs found
Magnetoresistance and spin polarization in the insulating regime of a Si two-dimensional electron system
We have studied the magnetoresistance in a high-mobility Si inversion layer
down to low electron concentrations at which the longitudinal resistivity
has an activated temperature dependence. The angle of the magnetic
field was controlled so as to study the orbital effect proportional to the
perpendicular component for various total strengths . A
dip in , which corresponds to the Landau level filling factor of
, survives even for high resistivity of at
. The linear -dependence of the value of
at the dip for low indicates that a ferromagnetic
instability does not occur even in the far insulating regime.Comment: 6 pages, 7 figures, submitted to PR
Inversion phenomenon and phase diagram of the distorted diamond chain with the interaction anisotropy
We discuss the anisotropies of the Hamiltonian and the wave-function in an
distorted diamond chain. The ground-state phase diagram of this model
is investigated using the degenerate perturbation theory up to the first order
and the level spectroscopy analysis of the numerical diagonalization data. In
some regions of the obtained phase diagram, the anisotropy of the Hamiltonian
and that of the wave-function are inverted, which we call inversion phenomenon;
the N\'{e}el phase appears for the XY-like anisotropy and the spin-fluid phase
appears for the Ising-like anisotropy. Three key words are important for this
nature, which are frustration, the trimer nature, and the anisotropy.Comment: 4pages, 10 figures, for proceedings of SPQS 200
Critical Properties of the transition between the Haldane phase and the large-D phase of the spin-1/2 ferromagnetic-antiferromagnetic Heisenberg chain with on-site anisotropy"
We analytically study the ground-state quantum phase transition between the
Haldane phase and the large- (LD) phase of the
ferromagnetic-antiferromagnetic alternating Heisenberg chain with on-site
anisotropy. We transform this model into a generalized version of the
alternating antiferromagnetic Heisenberg model with anisotropy. In the
transformed model, the competition between the transverse and longitudinal bond
alternations yields the Haldane-LD transition. Using the bosonization method,
we show that the critical exponents vary continuously on the Haldane-LD
boundary. Our scaling relations between critical exponents very well explains
the numerical results by Hida.Comment: text 12 pages (Plain TeX), LaTeX sourse files of a table and a figure
on reques
Equivalent hyperon-nucleon interactions in low-momentum space
Equivalent interactions in a low-momentum space for the , and interactions are calculated, using the SU quark model
potential as well as the Nijmegen OBEP model as the input bare interaction.
Because the two-body scattering data has not been accumulated sufficiently to
determine the hyperon-nucleon interactions unambiguously, the construction of
the potential even in low-energy regions has to rely on a theoretical model.
The equivalent interaction after removing high-momentum components is still
model dependent. Because this model dependence reflects the character of the
underlying potential model, it is instructive for better understanding of
baryon-baryon interactions in the strangeness sector to study the low-momentum
space interactions.Comment: 9 pages, 13 figures, accepted for publication in Phys. Rev.
Metal-Insulator Transition and Spin Degree of Freedom in Silicon 2D Electron Systems
Magnetotransport in 2DES's formed in Si-MOSFET's and Si/SiGe quantum wells at
low temperatures is reported. Metallic temperature dependence of resistivity is
observed for the n-Si/SiGe sample even in a parallel magnetic field of 9T,
where the spins of electrons are expected to be polarized completely.
Correlation between the spin polarization and minima in the diagonal
resistivity observed by rotating the samples for various total strength of the
magnetic field is also investigated.Comment: 3 pages, RevTeX, 4 eps-figures, conference paper (EP2DS-13
Theory of Mott insulator/band insulator heterostructure
A theory of heterostructures comprised of LaTiO (a Mott insulator) and
SrTiO (a band insulator) is presented. The band structure of the Ti %
-electrons is treated with a nearest neighbor tight-binding approximation; the
electric fields arising from the La/Sr charge difference and the
carriers are treated within a Hartree approximation; and the on-site
interactions are treated by unrestricted Hartree-Fock. The phase diagram as a
function of interaction strength and layer number is determined and predictions
are made for optical conductivity experiments. A note worthy finding is that
the edges of the heterostructure are generally metallic.Comment: 11 pages, 9 figure
A remark on the Hankel determinant formula for solutions of the Toda equation
We consider the Hankel determinant formula of the functions of the
Toda equation. We present a relationship between the determinant formula and
the auxiliary linear problem, which is characterized by a compact formula for
the functions in the framework of the KP theory. Similar phenomena that
have been observed for the Painlev\'e II and IV equations are recovered. The
case of finite lattice is also discussed.Comment: 14 pages, IOP styl
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