1,477 research outputs found
Determining the Electron-Phonon Coupling Strength in Correlated Electron Systems from Resonant Inelastic X-ray Scattering
We show that high resolution Resonant Inelastic X-ray Scattering (RIXS)
provides direct, element-specific and momentum-resolved information on the
electron-phonon (e-p) coupling strength. Our theoretical analysis demonstrates
that the e-p coupling can be extracted from RIXS spectra by determining the
differential phonon scattering cross section. An alternative, very direct
manner to extract the coupling is to use the one and two-phonon loss ratio,
which is governed by the e-p coupling strength and the core-hole life-time.
This allows measurement of the e-p coupling on an absolute energy scale.Comment: 4 pages, 3 figure
Spin and orbital dynamics through the metal-to-insulator transition in CdOsO probed with high-resolution RIXS
High-resolution resonant inelastic x-ray scattering (RIXS) measurements
(E = 46 meV) have been performed on CdOsO through the
metal-to-insulator transition (MIT). A magnetic excitation at 125 meV evolves
continuously through the MIT, in agreement with recent Raman scattering
results, and provides further confirmation for an all-in, all-out magnetic
ground state. Asymmetry of this feature is likely a result of coupling between
the electronic and magnetic degrees of freedom. We also observe a broad
continuum of interband excitations centered at 0.3 eV energy loss. This is
indicative of significant hybridization between Os 5 and O 2 states, and
concurrent itinerant nature of the system. In turn, this suggests a possible
break down of the free-ion model for CdOsO.Comment: Accepted in Physical Review B (10 pages
Going Dutch in the Mekong Delta:a framing perspective on water policy translation
In response to the rising climatic impacts on worldwide urbanized deltas, the Netherlands has strategically and politically framed Dutch water management as a global water solution for improving water safety and flood protection in other countries such as Vietnam. Being renowned for its water management approach, the Netherlands is particularly active in sharing water knowledge, insights, and policies internationally. This paper connects a framing perspective to policy translation studies to understand the role of language and meaning-making in the cross-border travel of policies. Adopting a framing perspective, it presents four dimensions of water policy translation concerning how policy frames are being created and interpreted - during the cross-border travel. The paper follows the process of the Dutch water management approach being 'packaged' as global water solutions and 'translated' to inform the development of the Vietnamese Mekong Delta Plan of 2013. The results show that although similar concepts, metaphors and narratives could be witnessed in this translation process, the local use and interpretation of these concepts remain challenging. Inclusive engagement, shared and comprehensive understanding, and continuous exchange and learning processes could help to improve cross-border policy-making for sustainable delta management
Orbital ordering in manganites in the band approach
We consider the orbital ordering in LaMnO3 and similar systems, proceeding
from the band picture. We show that for the realistic magnetic structure of
A-type there exists a complete nesting betweeen two e_g-bands. As a result
there occurs an instability towards an excitonic insulator-like state -- an
electron-hole pairing with the wave vector Q=(\pi,\pi), which opens a gap in
the spectrum and makes the system insulating. In the resulting state there
appeasr an orbital ordering -- orbital density wave (ODW), the type of which
coincides with those existing in LaMnO3.Comment: 4 pages, 2 figure
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Interactions between Affective and Cognitive Processing Systems in Problematic Gamblers: A Functional Connectivity Study
Background: Motivational and cognitive abnormalities are frequently reported in pathological gambling. However, studies simultaneously investigating motivational and cognitive processing in problematic gamblers are lacking, limiting our understanding of the interplay between these systems in problematic gambling. Studies in non-clinical samples indicate that interactions between dorsal “executive” and ventral “affective” processing systems are necessary for adequate responses in various emotive situations. Methods: We conducted a generalized Psycho-Physiological Interaction (gPPI) analysis to assess the influence of affective stimuli on changes in functional connectivity associated with response inhibition in 16 treatment seeking problematic gamblers (PRGs) and 15 healthy controls (HCs) using an affective Go-NoGo fMRI paradigm including neutral, gambling-related, positive and negative pictures as neutral and affective conditions. Results: Across groups, task performance accuracy during neutral inhibition trials was positively correlated with functional connectivity between the left caudate and the right middle frontal cortex. During inhibition in the gambling condition, only in PRGs accuracy of task performance was positively correlated with functional connectivity within sub-regions of the dorsal executive system. Group interactions showed that during neutral inhibition, HCs exhibited greater functional connectivity between the left caudate and occipital cortex than PRGs. In contrast, during inhibition in the positive condition, PRGs compared to HCs showed greater functional connectivity between the left caudate and occipital cortex. During inhibition trials in the negative condition, a stronger functional connectivity between the left caudate and the right anterior cingulate cortex in PRGs compared to HCs was present. There were no group interactions during inhibition in the gambling condition. Conclusions: During gamble inhibition PRGs seem to benefit more from functional connectivity within the dorsal executive system than HCs, because task accuracy in this condition in PRGs is positively correlated with functional connectivity, although the groups show similar connectivity patterns during gamble inhibition. Greater functional connectivity between the ventral affective system and the dorsal executive system in PRGs in the affective conditions compared to HCs, suggests facilitation of the dorsal executive system when affective stimuli are present specifically in PRGs
Bimagnon studies in cuprates with Resonant Inelastic X-ray Scattering at the O K edge. I - An assessment on La2CuO4 and a comparison with the excitation at Cu L3 and Cu K edges
We assess the capabilities of magnetic Resonant Inelastic X-ray Scattering
(RIXS) at the O edge in undoped cuprates by taking La_{2}CuO_{4} as a
benchmark case, based on a series of RIXS measurements that we present here. By
combining the experimental results with basic theory we point out the
fingerprints of bimagnon in the O edge RIXS spectra. These are a dominant
peak around 450 meV, the almost complete absence of dispersion both with
and polarization and the almost constant intensity vs. the transferred
momentum with polarization. This behavior is quite different from Cu
edge RIXS giving a strongly dispersing bimagnon tending to zero at the
center of the Brillouin zone. This is clearly shown by RIXS measurements at the
Cu edge that we present. The Cu bimagnon spectra and those at Cu
edge - both from the literature and from our data - however, have the same
shape. These similarities and differences are understood in terms of different
sampling of the bimagnon continuum. This panorama points out the unique
possibilities offered by O RIXS in the study of magnetic excitations in
cuprates near the center of the BZ
Momentum dependence of orbital excitations in Mott-insulating titanates
High-resolution resonant inelastic x-ray scattering has been used to
determine the momentum dependence of orbital excitations in Mott-insulating
LaTiO and YTiO over a wide range of the Brillouin zone. The data are
compared to calculations in the framework of lattice-driven and
superexchange-driven orbital ordering models. A superexchange model in which
the experimentally observed modes are attributed to two-orbiton excitations
yields the best description of the data.Comment: to appear in PR
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