311 research outputs found
Li intercalation effects on magnetism in undoped and Co-doped anatase TiO
The effects of -type carrier doping by Li intercalation on magnetism in
undoped and Co-doped anatase TiO are investigated. We have found that doped
-type carriers in TiO are localized mainly at Ti sites near the
intercalated Li. With increasing the intercalation, local spins are realized at
Ti. In the case of Co-doped TiO, most of the added -type carriers fill
the Co 3 bands and the rest are localized at Ti. Therefore, Co magnetic
moment vanishes by Li intercalation to have a nonmagnetic ground state.Comment: 6 pages, 2 figures, to appear in a special issue of Physica B,
proceedings of the 2nd Hiroshima Workshop on Transport and Thermal Properties
of Advanced Materials (Aug. 2002; Hiroshima, Japan
Overcharging of a macroion by an oppositely charged polyelectrolyte
The complexation of a polyelectrolyte with an oppositely charged spherical
macroion is studied for both salt free and salty solutions. When a
polyelectrolyte winds around the macroion, its turns repel each other and form
an almost equidistant coil. It is shown that this repulsive correlations of
turns lead to the charge inversion: more polyelectrolyte winds around the
macroion than it is necessary to neutralize it. The charge inversion becomes
stronger with increasing concentration of salt and can exceed 100%. This paper
confirms that correlations are the universal mechanism of charge inversion.Comment: Monte-Carlo simulation details added. Many corrections and references
added. Accepted to Physica
Internationalisation of Chinese SMEs: The Role of Networks and Global Value Chains
This article examines the role of networks and global value chains (GVCs), and how they influence emerging economy small and medium enterprisesā (EE-SMEs) internationalisation. Drawing on the insights, experiences and perspectives of entrepreneurs and senior managers of SMEs that have originated from China, the study adopts qualitative approach and examines nine firmsā internationalisation. We find that Chinese born-global manufacturing SMEs benefit from networks with quick insidership position into GVCs, but suffer from various obstacles that hinder their further development. The findings further indicate that network ties substantially facilitate EE-SMEsā internationalisation, but also restrict their future global development, as their low position within the GVCs impedes further business development and capability building. The case firmsā lower position within the GVCs weakens the networksā influence on their GVC upgrading. The research identifies key enablers of GVCs engagement and obstacles of GVCs upgrading of the case firms which play an important role in the EE-SMEsā internationalisation
Inversion of DNA charge by a positive polymer via fractionalization of the polymer charge
Charge inversion of a DNA double helix by an oppositely charged flexible
polyelectrolyte (PE) is widely used for gene delivery. It is considered here in
terms of discrete charges of DNA. We concentrate on the worst scenario case
when in the neutral state of the DNA-PE complex, each of the DNA charges is
locally compensated by a PE charge and show that charge inversion exists even
in this case. When an additional PE molecule is adsorbed by DNA, its charge
gets fractionalized into monomer charges of defects (tails and arches) on the
background of the perfectly neutralized DNA. These charges spread all over the
DNA eliminating the self-energy of PE. Fractionalization leads to a substantial
charge inversion of DNA. We show that fractionalization mechanism charge
inversion works also for nonlinear polymers such as dendrimers. Remarkably,
such fractionalization happens for adsorption of both PE or dendrimers on a
two-dimensional charged lattice, as well. Relation of fractionalization to
other mechanisms of charge inversion is discussed.Comment: Accepted for publication in Physica
Masses of composite fermions carrying two and four flux quanta: Differences and similarities
This study provides a theoretical rationalization for the intriguing
experimental observation regarding the equality of the normalized masses of
composite fermions carrying two and four flux quanta, and also demonstrates
that the mass of the latter type of composite fermion has a substantial filling
factor dependence in the filling factor range , in agreement
with experiment, originating from the relatively strong inter-composite fermion
interactions here.Comment: 5 pages, 2 figure
Beyond paired quantum Hall states: parafermions and incompressible states in the first excited Landau level
The Pfaffian quantum Hall states, which can be viewed as involving pairing
either of spin-polarized electrons or of composite fermions, are generalized by
finding the exact ground states of certain Hamiltonians with k+1-body
interactions, for all integers k > 0. The remarkably simple wavefunctions of
these states involve clusters of k particles, and are related to correlators of
parafermion currents in two-dimensional conformal field theory. The k=2 case is
the Pfaffian. For k > 1, the quasiparticle excitations of these systems are
expected to possess nonabelian statistics, like those of the Pfaffian. For k=3,
these ground states have large overlaps with the ground states of the (2-body)
Coulomb-interaction Hamiltonian for electrons in the first excited Landau level
at total filling factors \nu=2+3/5, 2+2/5.Comment: 11 pages Revtex in two column format with 4 eps figures included in
the M
Hamiltonian theory of gaps, masses and polarization in quantum Hall states: full disclosure
I furnish details of the hamiltonian theory of the FQHE developed with Murthy
for the infrared, which I subsequently extended to all distances and apply it
to Jain fractions \nu = p/(2ps + 1). The explicit operator description in terms
of the CF allows one to answer quantitative and qualitative issues, some of
which cannot even be posed otherwise. I compute activation gaps for several
potentials, exhibit their particle hole symmetry, the profiles of charge
density in states with a quasiparticles or hole, (all in closed form) and
compare to results from trial wavefunctions and exact diagonalization. The
Hartree-Fock approximation is used since much of the nonperturbative physics is
built in at tree level. I compare the gaps to experiment and comment on the
rough equality of normalized masses near half and quarter filling. I compute
the critical fields at which the Hall system will jump from one quantized value
of polarization to another, and the polarization and relaxation rates for half
filling as a function of temperature and propose a Korringa like law. After
providing some plausibility arguments, I explore the possibility of describing
several magnetic phenomena in dirty systems with an effective potential, by
extracting a free parameter describing the potential from one data point and
then using it to predict all the others from that sample. This works to the
accuracy typical of this theory (10 -20 percent). I explain why the CF behaves
like free particle in some magnetic experiments when it is not, what exactly
the CF is made of, what one means by its dipole moment, and how the comparison
of theory to experiment must be modified to fit the peculiarities of the
quantized Hall problem
Harmonic forcing of an extended oscillatory system: Homogeneous and periodic solutions
In this paper we study the effect of external harmonic forcing on a
one-dimensional oscillatory system described by the complex Ginzburg-Landau
equation (CGLE). For a sufficiently large forcing amplitude, a homogeneous
state with no spatial structure is observed. The state becomes unstable to a
spatially periodic ``stripe'' state via a supercritical bifurcation as the
forcing amplitude decreases. An approximate phase equation is derived, and an
analytic solution for the stripe state is obtained, through which the
asymmetric behavior of the stability border of the state is explained. The
phase equation, in particular the analytic solution, is found to be very useful
in understanding the stability borders of the homogeneous and stripe states of
the forced CGLE.Comment: 6 pages, 4 figures, 2 column revtex format, to be published in Phys.
Rev.
Partially spin polarized quantum Hall effect in the filling factor range 1/3 < nu < 2/5
The residual interaction between composite fermions (CFs) can express itself
through higher order fractional Hall effect. With the help of diagonalization
in a truncated composite fermion basis of low-energy many-body states, we
predict that quantum Hall effect with partial spin polarization is possible at
several fractions between and . The estimated excitation
gaps are approximately two orders of magnitude smaller than the gap at
, confirming that the inter-CF interaction is extremely weak in higher
CF levels.Comment: 4 pages, 3 figure
Spontaneous Pseudospin Spiral Order in Bilayer Quantum Hall Systems
Using exact diagonalization of bilayer quantum Hall systems at total filling
factor in the torus geometry, we show that there is a new long-range
interlayer phase coherence due to spontaneous pseudospin spiral order at
interlayer distances larger than the critical value at which the pseudospin
ferromagnetic order is destroyed. We emphasize the distinction between the
interlayer phase coherence and the pseudospin ferromagnetic order.Comment: 6 pages, 4 figures, Replaced by a new extended version published in
Phys. Rev.
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