19,152 research outputs found
Robustness of the nodal d-wave spectrum to strongly fluctuating competing order
We resolve an existing controversy between, on the one hand, convincing
evidence for the existence of competing order in underdoped cuprates, and, on
the other hand, spectroscopic data consistent with a seemingly homogeneous
d-wave superconductor in the very same compounds. Specifically, we show how
short-range fluctuations of the competing order essentially restore the nodal
d-wave spectrum from the qualitatively distinct folded dispersion resulting
from homogeneous coexisting phases. The signatures of the fluctuating competing
order can be found mainly in a splitting of the antinodal quasi-particles and,
depending of the strength of the competing order, also in small induced nodal
gaps as found in recent experiments on underdoped La{2-x}SrxCuO4.Comment: 5 pages, 4 figure
Signatures of orbital loop currents in the spatially resolved local density of states
Polarized neutron scattering measurements have suggested that intra-unit cell
antiferromagnetism may be associated with the pseudogap phase. Assuming that
loop current order is responsible for the observed magnetism, we calculate some
signatures of such circulating currents in the local density of states around a
single non-magnetic impurity in a coexistence phase with superconductivity. We
find a distinct C4 symmetry breaking near the disorder which is also detectable
in the resulting quasi-particle interference patterns.Comment: 5 pages, 3 figure
Many-Impurity Effects in Fourier Transform Scanning Tunneling Spectroscopy
Fourier transform scanning tunneling spectroscopy (FTSTS) is a useful
technique for extracting details of the momentum-resolved electronic band
structure from inhomogeneities in the local density of states due to
disorder-related quasiparticle scattering. To a large extent, current
understanding of FTSTS is based on models of Friedel oscillations near isolated
impurities. Here, a framework for understanding many-impurity effects is
developed based on a systematic treatment of the variance Delta rho^2(q,omega)
of the Fourier transformed local density of states rho(q,\omega). One important
consequence of this work is a demonstration that the poor signal-to-noise ratio
inherent in rho(q,omega) due to randomness in impurity positions can be
eliminated by configuration averaging Delta rho^2(q,omega). Furthermore, we
develop a diagrammatic perturbation theory for Delta rho^2(q,omega) and show
that an important bulk quantity, the mean-free-path, can be extracted from
FTSTS experiments.Comment: 7 pages, 5 figures. A version of the paper with high resolution,
colour figures is available at
http://www.trentu.ca/physics/batkinson/FTSTS.ps.gz minor revisions in
response to refree report + figure 5 is modifie
A study and evaluation of image analysis techniques applied to remotely sensed data
An analysis of phenomena causing nonlinearities in the transformation from Landsat multispectral scanner coordinates to ground coordinates is presented. Experimental results comparing rms errors at ground control points indicated a slight improvement when a nonlinear (8-parameter) transformation was used instead of an affine (6-parameter) transformation. Using a preliminary ground truth map of a test site in Alabama covering the Mobile Bay area and six Landsat images of the same scene, several classification methods were assessed. A methodology was developed for automatic change detection using classification/cluster maps. A coding scheme was employed for generation of change depiction maps indicating specific types of changes. Inter- and intraseasonal data of the Mobile Bay test area were compared to illustrate the method. A beginning was made in the study of data compression by applying a Karhunen-Loeve transform technique to a small section of the test data set. The second part of the report provides a formal documentation of the several programs developed for the analysis and assessments presented
On the precision of chiral-dispersive calculations of scattering
We calculate the combination (the Olsson sum rule)
and the scattering lengths and effective ranges , and ,
dispersively (with the Froissart--Gribov representation) using, at
low energy, the phase shifts for scattering obtained by Colangelo,
Gasser and Leutwyler (CGL) from the Roy equations and chiral perturbation
theory, plus experiment and Regge behaviour at high energy, or directly, using
the CGL parameters for s and s. We find mismatch, both among the CGL
phases themselves and with the results obtained from the pion form factor. This
reaches the level of several (2 to 5) standard deviations, and is essentially
independent of the details of the intermediate energy region ( GeV) and, in some cases, of the high energy behaviour assumed. We discuss
possible reasons for this mismatch, in particular in connection with an
alternate set of phase shifts.Comment: Version to appear in Phys. Rev. D. Graphs and sum rule added. Plain
TeX fil
Classification software technique assessment
A catalog of software options is presented for the use of local user communities to obtain software for analyzing remotely sensed multispectral imagery. The resources required to utilize a particular software program are described. Descriptions of how a particular program analyzes data and the performance of that program for an application and data set provided by the user are shown. An effort is made to establish a statistical performance base for various software programs with regard to different data sets and analysis applications, to determine the status of the state-of-the-art
Studies on optimizing potential energy functions for maximal intrinsic hyperpolarizability
We use numerical optimization to study the properties of (1) the class of
one-dimensional potential energy functions and (2) systems of point charges in
two-dimensions that yield the largest hyperpolarizabilities, which we find to
be within 30% of the fundamental limit. We investigate the character of the
potential energy functions and resulting wavefunctions and find that a broad
range of potentials yield the same intrinsic hyperpolarizability ceiling of
0.709.Comment: 9 pages, 9 figure
Local transport in a disorder-stabilized correlated insulating phase
We report the experimental realization of a correlated insulating phase in 2D
GaAs/AlGaAs heterostructures at low electron densities in a limited window of
background disorder. This has been achieved at mesoscopic length scales, where
the insulating phase is characterized by a universal hopping transport
mechanism. Transport in this regime is determined only by the average electron
separation, independent of the topology of background disorder. We have
discussed this observation in terms of a pinned electron solid ground state,
stabilized by mutual interplay of disorder and Coulomb interaction.Comment: 4+delta pages, 4 figures, To appear in the Physical Review B (Rapid
Comm
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