2,239 research outputs found
Crystal cleaving machine
A machine is disclosed for cleaving hard crystals. A typical example of which is lithium fluoride, with prcision and uniformity and includes vertical axis positioning control means for an adjustable spring tension guided hammer mechanism employed to strike an anvil. A crystal cleaving shock wave transmitted to a cleaving blade is generated having an angulated cleaving edge in contact with one corner of the crystal. Connection between the anvil and the blade is by means of a pair of vertical shafts held in substantially friction free engagement by two pairs of adjustable linear bearings. An underlying crystal holding fixture with horizontal position control means includes a zero reference stop face for the crystal and opposing spring-loaded clamping and vertical positioning elements which are precisely guided
Fused Azulenes: Possible Organic Multiferroics
We present compelling theoretical results showing that fused azulene
molecules are strong candidates for exhibiting room temperature multiferroic
behavior, i.e., having both, ferroelectric and ferromagnetic properties. If
this is experimentally proved, these systems will be the first organic
multiferroic materials with important potential applications.Comment: 4 pages, 4 figure
Mergers & Abenomics: The Determinants of M&A in Japan\u27s New Economy
This paper investigates the influence of various macroeconomic variables on Japan’s merger and acquisition (M&A) activity, both in terms of total deal value and total number of deals. Looking at monthly data from June 1997 to December 2013, I use econometric time-series analysis to find that: First, total deal value per month is not well explained by our macroeconomic variables, but about half of the variation in number of deals per month can be explained by our dataset. Second, the most important determinant in the total number of deals per month during our period is the level of national debt, and interest rates had the opposite effect from what was originally expected. Third, adding lag variables to our analysis proved to be relatively fruitless. Finally, when taking a look at only the past couple of years to determine the effects of “Abenomics” on M&A activity in Japan, I conclude that there is not enough data, and better results would be obtained in the future
Method and apparatus for slicing crystals
The crystal slicing method is described as follows. A crystal is sliced in a plane parallel to flat, opposed parallel end faces of the crystal. The end faces of the crystal are gripped by a pair of opposed, perforated platens of a pair of vacuum chambers, one of which is translatable relative to the other. A blade cuts the crystal through the desired plane. A spring biases one of the vacuum chambers away from the other vacuum chamber while both of the faces are gripped by the vacuum chambers and the blade is cleaving the crystal. A sliced portion of the crystal gripped by one of the vacuum chambers is pulled away from the remainder of the crystal gripped by the second vacuum chamber when the crystal was cleaved by the blade through the plane
Spin filters with Fano dots
We compute the zero bias conductance of electrons through a single ballistic
channel weakly coupled to a side quantum dot with Coulomb interaction. In
contrast to the standard setup which is designed to measure the transport
through the dot, the channel conductance reveals Coulomb blockade dips rather
then peaks due to the Fano-like backscattering. At zero temperature the Kondo
effect leads to the formation of broad valleys of small conductance
corresponding to an odd number of electrons on the dot. By applying a magnetic
field in the dot region we find two dips corresponding to a total suppression
in the conductance of spins up and down separated by an energy of the order of
the Coulomb interaction. This provides a possibility of a perfect spin filter.Comment: 5 pages, 4 figures, to be published in European Physical Journal
State-of-the-art techniques for calculating spectral functions in models for correlated materials
The dynamical mean field theory (DMFT) has become a standard technique for
the study of strongly correlated models and materials overcoming some of the
limitations of density functional approaches based on local approximations. An
important step in this method involves the calculation of response functions of
a multiorbital impurity problem which is related to the original model.
Recently there has been considerable progress in the development of techniques
based on the density matrix renormalization group (DMRG) and related matrix
product states (MPS) implying a substantial improvement to previous methods. In
this article we review some of the standard algorithms and compare them to the
newly developed techniques, showing examples for the particular case of the
half-filled two-band Hubbard model.Comment: 8 pages, 4 figures, to be published in EPL Perspective
Exact Correlation Amplitude for the S=1/2 Heisenberg Antiferromagnetic Chain
The exact amplitude for the asymptotic correlation function in the S=1/2
Heisenberg antiferromagnetic chain is determined: goes to (-1)^r
delta^{ab}(ln r)^{1/2}/[(2 pi)^{3/2}r]. The behaviour of the correlation
functions for small xxz anisotropy and the form of finite-size corrections to
the correlation function are also analysed.Comment: 8 pages, 3 figures, added reference and discussio
Response of finite spin-S Heisenberg chains to local perturbations
We consider the properties of finite isotropic antiferromagnetic Heisenberg
chains with S=1/2, 1, 3/2 spins when a weak magnetic field is applied on a few
sites, using White's density matrix renormalization group (DMRG) method. For
the S=1 chain there exists only one length scale in the system which determines
the behavior of the one- and two-point correlation functions both around the
local perturbation and near the free boundary. For the critical,
half-odd-integer spin cases the exponent of the spin-spin correlation function
was found to be , and the exponent of the decay of the site
magnetization around the perturbed site is . Close to a free
boundary, however, the behavior is completely different for S=1/2 and .Comment: 13 pages, 7 figure
Spin-orbit coupling and electron spin resonance for interacting electrons in carbon nanotubes
We review the theoretical description of spin-orbit scattering and electron
spin resonance in carbon nanotubes. Particular emphasis is laid on the effects
of electron-electron interactions. The spin-orbit coupling is derived, and the
resulting ESR spectrum is analyzed both using the effective low-energy field
theory and numerical studies of finite-size Hubbard chains and two-leg Hubbard
ladders. For single-wall tubes, the field theoretical description predicts a
double peak spectrum linked to the existence of spin-charge separation. The
numerical analysis basically confirms this picture, but also predicts
additional features in finite-size samples.Comment: 19 pages, 4 figures, invited review article for special issue in J.
Phys. Cond. Mat., published versio
Numerical renormalization group study of the correlation functions of the antiferromagnetic spin- Heisenberg chain
We use the density-matrix renormalization group technique developed by White
\cite{white} to calculate the spin correlation functions
for isotropic Heisenberg rings up to
sites. The correlation functions for large and are found to obey
the scaling relation
proposed by Kaplan et al. \cite{horsch} , which is used to determine
. The asymptotic correlation function and
the magnetic structure factor show logarithmic corrections
consistent with , where is related
to the cut-off dependent coupling constant , as
predicted by field theoretical treatments.Comment: Accepted in Phys. Rev. B. 4 pages of text in Latex + 5 figures in
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