1,305 research outputs found
Electron-phonon coupling and spin-charge separation in one-dimensional Mott insulators
We examine the single-particle excitation spectrum in the one-dimensional
Hubbard-Holstein model at half-filling by performing the dynamical density
matrix renormalization group (DDMRG) calculation. The DDMRG results are
interpreted as superposition of spectra for a spinless carrier dressed with
phonons. The superposition is a consequence of robustness of the spin-charge
separation against electron-phonon coupling. The separation is in contrast to
the coupling between phonon and spin degrees of freedom in two-dimensional
systems. We discuss implication of the results of the recent angle-resolved
photoemission spectroscopy measurements on SrCuO.Comment: 5 pages, 4 figures. submitted to the Physical Review Letter
Critical behavior of the S=3/2 antiferromagnetic Heisenberg chain
Using the density-matrix renormalization-group technique we study the
long-wavelength properties of the spin S=3/2 nearest-neighbor Heisenberg chain.
We obtain an accurate value for the spin velocity v=3.8+- 0.02, in agreement
with experiment. Our results show conclusively that the model belongs to the
same universality class as the S=1/2 Heisenberg chain, with a conformal central
charge c=1 and critical exponent eta=1Comment: RevTeX (version 3.0), 4 twocolumn pages with 4 embedded figure
Brief report: Maternal posttraumatic stress symptoms are related to adherence to their child's diabetes treatment regimen.
Although research suggests that posttraumatic stress disorder symptoms in relation to physical health diagnoses may be related to poor adherence to treatment regimens, so far, whether parental posttraumatic stress disorder symptoms have an impact on their child's adherence to insulin-dependent diabetes mellitus treatment has not been investigated. Using self-report questionnaires, the present study found that children of mothers who have posttraumatic stress disorder symptoms in relation to their child's diagnosis of type I diabetes showed poorer adherence to treatment than the children of mothers without posttraumatic stress disorder. However, this was only the case for younger children (aged 0-8 years) where mothers played a more active role in their child's treatment
The psychological impact of stillbirth on women: a systematic review.
This systematic review explored the psychological impact of stillbirth (from
20 weeks gestation) on mothers. A search was conducted in the National
Library for Health and Web of Science, Cochrane Review, and Google
Scholar. A secondary search based on results from the preliminary search was
undertaken. A systematic search identified 26 articles (8 qualitative, 18
quantitative studies), which met criteria and were reviewed according to
guidelines. The findings revealed that stillbirth is a distressing experience that
can result in high levels of psychological symptoms including anxiety,
depression, distress, and negative well-being. Symptoms appear to be highest
in the first few months post loss although there is evidence to suggest that for
some, symptoms may persist up to 3 years. The long-lasting impact of
stillbirth on women was echoed in the qualitative research. Risk factors for
higher levels of anxious and depressive symptoms included higher parity at
the time of loss and not being married. Social support in particular was
identified to be beneficial for women post loss. Longitudinal studies utilizing
designs which permit causality to be determined are required to explore the
specific experience of stillbirth. Further exploration of risk and protective
factors, cultural beliefs, and the impact on partner relationships is needed.
Clinical implications of the findings are discussed in light of current guidance
Polaron in t-J model
We present numeric results for ground state and angle resolved photoemission
spectra (ARPES) for single hole in t-J model coupled to optical phonons. The
systematic-error free diagrammatic Monte Carlo is employed where the Feynman
graphs for the Matsubara Green function in imaginary time are summed up
completely with respect to phonons variables, while magnetic variables are
subjected to non-crossing approximation. We obtain that at electron-phonon
coupling constants relevant for high Tc cuprates the polaron undergoes
self-trapping crossover to strong coupling limit and theoretical ARPES
demonstrate features observed in experiment: a broad peak in the bottom of the
spectra has momentum dependence which coincides with that of hole in pure t-J
model.Comment: 4 pages, 4 figure
Anisotropic optical response of the mixed-valent Mott-Hubbard insulator NaCu2O2
We report the results of a comprehensive spectroscopic ellipsometry study of
NaCu2O2, a compound composed of chains of edge-sharing Cu2+O4 plaquettes and
planes of Cu1+ ions in a O-Cu1+-O dumbbell configuration, in the spectral range
0.75-6.5 eV at temperatures 7 -300 K. The spectra of the dielectric function
for light polarized parallel to the Cu1+ planes reveal a strong in-plane
anisotropy of the interband excitations. Strong and sharp absorption bands
peaked at 3.45 eV (3.7 eV) dominate the spectra for polarization along
(perpendicular) to the Cu2+O2 chains. They are superimposed on flat and
featureless plateaux above the absorption edges at 2.25 eV (2.5 eV). Based on
density-functional calculations, the anomalous absorption peaks can be assigned
to transitions between bands formed by Cu1+ 3dxz(dyz) and Cu2+ 3dxy orbitals,
strongly hybridized with O pstates. The major contribution to the background
response comes from transitions between Cu1+ 3dz2 and 4px(py) bands. This
assignment accounts for the measured in-plane anisotropy. The dielectric
response along the Cu2+O2 chains develops a weak two-peak structure centered at
2.1 and 2.65 eV upon cooling below 100 K, along with the appearance of spin
correlations along the Cu2+O2 chains. These features bear a striking
resemblance to those observed in the single-valent Cu2+O2 chain compound
LiCuVO4, which were identified as an exciton doublet associated with
transitions to the upper Hubbard band that emerges as a consequence of the
long-range Coulomb interaction between electrons on neighboring Cu2+ sites
along the chains. An analysis of the spectral weights of these features yields
the parameters characterizing the on-site and long-range Coulomb interactions.Comment: 12 pages, 12 figure
Exciton doublet in the Mott-Hubbard LiCuVO insulator identified by spectral ellipsometry
Spectroscopic ellipsometry was used to study the dielectric function of
LiCuVO, a compound comprised of chains of edge-sharing CuO
plaquettes, in the spectral range (0.75 - 6.5) eV at temperatures (7-300) K.
For photon polarization along the chains, the data reveal a weak but
well-resolved two-peak structure centered at 2.15 and 2.95 eV whose spectral
weight is strongly enhanced upon cooling near the magnetic ordering
temperature. We identify these features as an exciton doublet in the
Mott-Hubbard gap that emerges as a consequence of the Coulomb interaction
between electrons on nearest and next-nearest neighbor sites along the chains.
Our results and methodology can be used to address the role of the long-range
Coulomb repulsion for compounds with doped copper-oxide chains and planes.Comment: 4 pages with 4 figures and EPAPS supplementary online material (3
pages with 4 figures), accepted in Phys. Rev. Let
Posttraumatic stress disorder in mothers of individuals with Anorexia Nervosa.
This pilot study aimed to investigate the prevalence of maternal posttraumatic stress (PTSD), anxiety and depressive symptoms and what aspects of having a child with anorexia nervosa (AN) are perceived as traumatic by the mothers. Thirty-one mothers of daughters with AN completed a range of self-report questionnaires and a structured clinical interview. Higher rates of anxiety, depression and PTSD symptoms were found in mothers than in the general UK population. Mothers reported acute traumatic stressors during the course of AN, such as 'thinking their daughter was about to die or dead', 'seeing or consenting to their daughter being tube-fed'. We also found that mothers rated chronic aspects of their daughter's AN as very severely distressing, such as 'worrying about permanent damage to daughter's health'. Results suggest that maternal mental health should be kept in mind during assessments of individuals with eating disorders and referral for a service in their own right might be indicated
Credit Information Sharing and Its Link to Financial Inclusion and Financial Intermediation
In this article, several regression analyses are conducted to analyse the relationship of credit information sharing
(by both private credit bureaus and public credit registries) with financial inclusion and financial intermediation.
We find that there is a positive relationship between information sharing mechanisms and financial
inclusion (measured by account (at a financial institution), borrowed from a financial institution, and domestic
credit). We do not find significant results for bank performance parameters. Whereas this is the case with bank
non-performing loans, the data do not allow (due to low R2) drawing conclusions on other parameters such as
lending minus inflation rate or bank concentration
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