31,718 research outputs found
Field Effect Transistors on Rubrene Single Crystals with Parylene Gate Insulator
We report on fabrication and characterization of the organic field effect
transistors (OFETs) on the surface of single crystals of rubrene. The parylene
polymer film has been used as the gate insulator. At room temperature, these
OFETs exhibit the p-type conductivity with the field effect mobility up to 1
cm^2/Vs and the on/off ratio ~ 10^4. The temperature dependence of the mobility
is discussed.Comment: 3 page
Universality and universal finite-size scaling functions in four-dimensional Ising spin glasses
We study the four-dimensional Ising spin glass with Gaussian and bond-diluted
bimodal distributed interactions via large-scale Monte Carlo simulations and
show via an extensive finite-size scaling analysis that four-dimensional Ising
spin glasses obey universality.Comment: 12 pages, 9 figures, 4 table
Vortex liquid crystals in anisotropic type II superconductors
In a type II superconductor in a moderate magnetic field, the superconductor
to normal state transition may be described as a phase transition in which the
vortex lattice melts into a liquid. In a biaxial superconductor, or even a
uniaxial superconductor with magnetic field oriented perpendicular to the
symmetry axis, the vortices acquire elongated cross sections and interactions.
Systems of anisotropic, interacting constituents generally exhibit liquid
crystalline phases. We examine the possibility of a two step melting in
homogeneous type II superconductors with anisotropic superfluid stiffness from
a vortex lattice into first a vortex smectic and then a vortex nematic at high
temperature and magnetic field. We find that fluctuations of the ordered phase
favor an instability to an intermediate smectic-A in the absence of intrinsic
pinning
Effect of interchain coupling on conducting polymer luminescence: excimers in derivatives of poly(phenylene vinylene)
Optical excitation of a chain in a polymer film may result in formation of an
excimer, a superposition of on-chain excitons and charge-transfer excitons on
the originally excited chain and a neighboring chain. The excimer emission is
red-shifted compared to that of an on-chain exciton by an amount depending on
the interchain coupling . Setting up the excimer wavefunction and
calculating the red shift, we determine average values, referred to a
monomer, of 0.52 eV and 0.16 eV for poly(2,5-hexyloxy -phenylene
cyanovinylene), CN-PPV, and poly[2-methoxy, 5-(2'-ethyl-hexyloxy)-1, 4
p-phenylene vinylene], MEH-PPV, respectively, and use them to determine the
effect of interchain distance on the emission.Comment: 10 pages, RevTeX, 1 PS figure, replaced version of cond-mat/9707095,
accepted for publication in Phys. Rev. B, Rapid Communicatio
On the sigma-model structure of type IIA supergravity action in doubled field approach
In this letter we describe how to string together the doubled field approach
by Cremmer, Julia, Lu and Pope with Pasti-Sorokin-Tonin technique to construct
the sigma-model-like action for type IIA supergravity. The relation of the
results with that of obtained in the context of searching for
Superstring/M-theory hidden symmetry group is discussed.Comment: 9 pp, LATEX; published in JETP Let
An extended scaling analysis of the S=1/2 Ising ferromagnet on the simple cubic lattice
It is often assumed that for treating numerical (or experimental) data on
continuous transitions the formal analysis derived from the Renormalization
Group Theory can only be applied over a narrow temperature range, the "critical
region"; outside this region correction terms proliferate rendering attempts to
apply the formalism hopeless. This pessimistic conclusion follows largely from
a choice of scaling variables and scaling expressions which is traditional but
which is very inefficient for data covering wide temperature ranges. An
alternative "extended caling" approach can be made where the choice of scaling
variables and scaling expressions is rationalized in the light of well
established high temperature series expansion developments. We present the
extended scaling approach in detail, and outline the numerical technique used
to study the 3d Ising model. After a discussion of the exact expressions for
the historic 1d Ising spin chain model as an illustration, an exhaustive
analysis of high quality numerical data on the canonical simple cubic lattice
3d Ising model is given. It is shown that in both models, with appropriate
scaling variables and scaling expressions (in which leading correction terms
are taken into account where necessary), critical behavior extends from Tc up
to infinite temperature.Comment: 16 pages, 17 figure
Protecting the Primordial Baryon Asymmetry From Erasure by Sphalerons
If the baryon asymmetry of the universe was created at the GUT scale,
sphalerons together with exotic sources of -violation could have erased
it, unless the latter satisfy stringent bounds. We elaborate on how the small
Yukawa coupling of the electron drastically weakens previous estimates of these
bounds.Comment: 41 pp., 4 latex figures included and 3 uuencoded or postscript
figures available by request, UMN-TH-1213-9
On dynamical mass generation in three dimensional supersymmetric U(1) gauge field theory
We investigate and contrast the non-perturbative infra red structure of N=1
and N=2 supersymmetric non-compact U(1) gauge field theory in three space-time
dimensions with N matter flavours. We study the Dyson-Schwinger equations in a
general gauge using superfield formalism; this ensures that supersymmetry is
kept manifest, though leads to spurious infra red divergences which we have to
avoid carefully. In the N=1 case the superfield formalism allows us to choose a
vertex which satisfies the U(1) Ward identity exactly, and we find the expected
critical behaviour in the wavefunction renormalization and strong evidence for
the existence of a gauge independent dynamically generated mass, but with no
evidence for a critical flavour number. We study the N=2 model by dimensional
reduction from four dimensional N=1 electrodynamics, and we refine the old
gauge dependence argument that there is no dynamical mass generation. We
recognize that the refinement only holds after dimensional reduction.Comment: 32 pages RevTeX; 3 axodraw figures include
Static Chaos in Spin Glasses against quenched disorder perturbations
We study the chaotic nature of spin glasses against perturbations of the
realization of the quenched disorder. This type of perturbation modifies the
energy landscape of the system without adding extensive energy. We exactly
solve the mean-field case, which displays a very similar chaos to that observed
under magnetic field perturbations, and discuss the possible extension of these
results to the case of short-ranged models. It appears that dimension four
plays the role of a specific critical dimension where mean-field theory is
valid. We present numerical simulation results which support our main
conclusions.Comment: 13 Pages + 7 Figures, Latex File, figures uuencoded at end of fil
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