939 research outputs found
Photoemission view of electron fractionalization in quasi-one dimensional metal LiMoO
We report Luttinger liquid line shapes better revealed by new angle resolved
photoemission data taken with a much improved angle resolution on a
quasi-1-dimensional metal LiMoO. The new data indicate a
larger spinon velocity than our previous lower resolution data indicated.Comment: submitted to SCES '0
Nearest Labelset Using Double Distances for Multi-label Classification
Multi-label classification is a type of supervised learning where an instance
may belong to multiple labels simultaneously. Predicting each label
independently has been criticized for not exploiting any correlation between
labels. In this paper we propose a novel approach, Nearest Labelset using
Double Distances (NLDD), that predicts the labelset observed in the training
data that minimizes a weighted sum of the distances in both the feature space
and the label space to the new instance. The weights specify the relative
tradeoff between the two distances. The weights are estimated from a binomial
regression of the number of misclassified labels as a function of the two
distances. Model parameters are estimated by maximum likelihood. NLDD only
considers labelsets observed in the training data, thus implicitly taking into
account label dependencies. Experiments on benchmark multi-label data sets show
that the proposed method on average outperforms other well-known approaches in
terms of Hamming loss, 0/1 loss, and multi-label accuracy and ranks second
after ECC on the F-measure
Luttinger liquid ARPES spectra from samples of LiMoO grown by the temperature gradient flux technique
Angle resolved photoemission spectroscopy line shapes measured for
quasi-one-dimensional LiMoO samples grown by a temperature
gradient flux technique are found to show Luttinger liquid behavior, consistent
with all previous data by us and other workers obtained from samples grown by
the electrolyte reduction technique. This result eliminates the sample growth
method as a possible origin of considerable differences in photoemission data
reported in previous studies of LiMoO.Comment: Some text adde
Seasonal Decomposition for Geographical Time Series using Nonparametric Regression
A time series often contains various systematic effects such as trends and seasonality. These different components can be determined and separated by decomposition methods. In this thesis, we discuss time series decomposition process using nonparametric regression. A method based on both loess and harmonic regression is suggested and an optimal model selection method is discussed. We then compare the process with seasonal-trend decomposition by loess STL (Cleveland, 1979). While STL works well when that proper parameters are used, the method we introduce is also competitive: it makes parameter choice more automatic and less complex. The decomposition process often requires that time series be evenly spaced; any missing value is therefore necessarily estimated. For time series with seasonality, it is preferable to use the seasonal information to estimate missing observations. The seasonal adjustment algorithm (McLeod et al., 1983) can be used for monthly time series. In this thesis, we examine the algorithm and revise it to cover daily data cases
Hidden one-dimensional electronic structure and non-Fermi liquid angle resolved photoemission line shapes of -MoO
We report angle resolved photoemission (ARPES) spectra of
-MoO, a layered metal that undergoes two charge density wave
(CDW) transitions at 109 K and 30 K. We have directly observed the ``hidden
one-dimensional (hidden-1d)'' Fermi surface and an anisotropic gap opening
associated with the 109 K transition, in agreement with the band theoretical
description of the CDW transition. In addition, as in other hidden-1d materials
such as NaMoO, the ARPES line shapes show certain anomalies, which
we discuss in terms of non-Fermi liquid physics and possible roles of disorder.Comment: 3 figures; Erratum added to include missed reference
Generalized Spectral Signatures of Electron Fractionalization in Quasi-One and -Two Dimensional Molybdenum Bronzes and Superconducting Cuprates
We establish the quasi-one-dimensional Li purple bronze as a photoemission
paradigm of Luttinger liquid behavior. We also show that generalized signatures
of electron fractionalization are present in the angle resolved photoemission
spectra for quasi-two-dimensional purple bronzes and certain cuprates. An
important component of our analysis for the quasi-two-dimensional systems is
the proposal of a ``melted holon'' scenario for the k-independent background
that accompanies but does not interact with the peaks that disperse to define
the Fermi surface.Comment: 7 pages, 8 figure
Extremely Correlated Fermi Liquid Description of Normal State ARPES in Cuprates
The normal state single particle spectral function of the high temperature
superconducting cuprates, measured by the angle resolved photoelectron
spectroscopy (ARPES), has been considered both anomalous and crucial to
understand. Here we show that an unprecedentedly detailed description of the
data is provided by a spectral function arising from the Extremely Correlated
Fermi Liquid state of the t-J model proposed recently by Shastry. The
description encompasses both laser and conventional synchrotron ARPES data on
optimally doped BiSrCaCuO, and also conventional
synchrotron ARPES data on the LaSrCuO materials. {\em It
fits all data sets with the same physical parameter values}, satisfies the
particle sum rule and successfully addresses two widely discussed "kink"
anomalies in the dispersion.Comment: Published version, 5 figs; published 29 July (2011
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