135,788 research outputs found
Chiral charge-density-waves
We discovered the chirality of charge density waves (CDW) in 1T-TiSe by
using scanning tunnelling microscopy (STM) and optical ellipsometry. We found
that the CDW intensity becomes , where (i =1, 2, 3) is the amplitude of the tunnelling current
contributed by the CDWs. There were two states, in which the three intensity
peaks of the CDW decrease \textit{clockwise} and \textit{anticlockwise} when we
index each nesting vector in order of intensity in the Fourier transformation
of the STM images. The chirality in CDW results in the three-fold symmetry
breaking. Macroscopically, two-fold symmetry was indeed observed in optical
measurement. We propose the new generalized CDW chirality H_{CDW} \equiv
{\boldmath q_1} \cdot ({\boldmath q_2}\times {\boldmath q_3}), where
{\boldmath q_i} are the nesting vectors, which is independent of the
symmetry of components. The nonzero - the triple-{\boldmath q}
vectors do not exist in an identical plane in the reciprocal space - should
induce a real-space chirality in CDW system.Comment: 12 pages, 4 figure
Holographic Charge Density Waves
We discuss a gravity dual of a charge density wave consisting of a U(1) gauge
field and two scalar fields in the background of an AdS Schwarzschild black
hole together with an antisymmetric field (probe limit). Interactions drive the
system to a phase transition below a critical temperature. We numerically
compute the ground states characterized by modulated solutions for the gauge
potential corresponding to a dynamically generated unidirectional charge
density wave in the conformal field theory. Signatures of the holographic
density waves are retrieved by studying the dynamical response to an external
electric field. We find that this novel holographic state shares many common
features with the standard condensed matter version of charge density wave
systems.Comment: 5 pages, 2 figures; improved discussion, published versio
Charge Density Wave Ratchet
We propose to operate a locally-gated charge density wave as an electron
pump. Applying an oscillating gate potential with frequency causes equally
spaced plateaux in the sliding charge density wave current separated by where is the number of parallel chains. The effects of thermal
noise are investigated.Comment: To be published in Applied Physics Letter
Charge Density of the Neutron
A model-independent analysis of the infinite-momentum-frame charge density of
partons in the transverse plane is presented for the nucleon. We find that the
neutron parton charge density is negative at the center, so that the square of
the transverse charge radius is positive, in contrast with many expectations.
Additionally, the proton's central u quark charge density is larger than that
of the d quark by about 70 %. The proton (neutron) charge density has a long
range positively (negatively) charged component.Comment: 7 pages, three figures The replacement mainly concerns correcting an
error made in computing the proton up and down quark densities from the
correctly computed proton and neutron charge densities. The proton central u
quark density is now larger than that of the d quar
Polyelectrolytes with high charge density
Polymers can be used as flocculants to clarify residential and industrial water supplies and as bactericidal and fungicidal agents. They can be used in preparation of electroconductive photocopy papers, to improve living cell adhesion to glass or plastic, and as anticancer agents
Electrostatic interactions in host-guest complexes 2
In this article the quantum chemically calculated charge density distribution of 18-crown-6 and the K+ 18-crown-6 complex are compared with the charge density distribution of smaller molecules and corresponding complexes which can be considered as fragments of the 18-crown-6 molecule. An analysis of the charge density distribution in terms of atomic charge distribution according to the stockholder recipe gives accurate rules for the transferability of the charge density distribution. This gives us the possibility to construct the charge density distribution of large molecules out of accurate large basis set results on small molecules
Charge density wave in hidden order state of URuSi
We argue that the hidden order state in URuSi will induce a charge
density wave. The modulation vector of the charge density wave will be twice
that of the hidden order state, . To illustrate how the
charge density wave arises we use a Ginzburg-Landau theory that contains a
coupling of the charge density wave amplitude to the square of the HO order
parameter . This simple analysis allows us to predict the
intensity and temperature dependence of the charge density wave order parameter
in terms of the susceptibilities and coupling constants used in the
Ginzburg-Landau analysis.Comment: 8 pages, 4 figure
Quantum crystallographic charge density of urea
Standard X-ray crystallography methods use free-atom models to calculate mean
unit cell charge densities. Real molecules, however, have shared charge that is
not captured accurately using free-atom models. To address this limitation, a
charge density model of crystalline urea was calculated using high-level
quantum theory and was refined against publicly available ultra high-resolution
experimental Bragg data, including the effects of atomic displacement
parameters. The resulting quantum crystallographic model was compared to models
obtained using spherical atom or multipole methods. Despite using only the same
number of free parameters as the spherical atom model, the agreement of the
quantum model with the data is comparable to the multipole model. The static,
theoretical crystalline charge density of the quantum model is distinct from
the multipole model, indicating the quantum model provides substantially new
information. Hydrogen thermal ellipsoids in the quantum model were very similar
to those obtained using neutron crystallography, indicating that quantum
crystallography can increase the accuracy of the X-ray crystallographic atomic
displacement parameters. The results demonstrate the feasibility and benefits
of integrating fully periodic quantum charge density calculations into ultra
high-resolution X-ray crystallographic model building and refinement.Comment: 40 pages, 4 figures, 6 table
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