126 research outputs found
Anisotropic damping and wave vector dependent susceptibility of the spin fluctuations in La2-xSrxCuO4 studied by resonant inelastic x-ray scattering
We report high-resolution resonant inelastic x-ray scattering (RIXS)
measurements of the collective spin fluctuations in three compositions of the
superconducting cuprate system La2-xSrxCuO4. We have mapped out the excitations
throughout much of the 2-D (h,k) Brillouin zone. The spin fluctuations in
La2-xSrxCuO4 are found to be fairly well-described by a damped harmonic
oscillator model, thus our data allows us to determine the full wavevector
dependence of the damping parameter. This parameter increases with doping and
is largest along the (h, h) line, where it is peaked near (0.2,0.2). We have
used a new procedure to determine the absolute wavevector-dependent
susceptibility for the doped compositions La2-xSrxCuO4 (x=0.12,0.16) by
normalising our data to La2CuO4 measurements made with inelastic neutron
scattering (INS). We find that the evolution with doping of the intensity of
high-energy excitations measured by RIXS and INS is consistent. For the doped
compositions, the wavevector-dependent susceptibility is much larger at
(1/4,1/4) than at (1/2,0). It increases rapidly along the (h,h) line towards
the antiferromagnetic wavevector of the parent compound (1/2,1/2). Thus, the
strongest magnetic excitations, and those predicted to favour superconductive
pairing, occur towards the (1/2,1/2) position as observed by INS
Dynamical spin susceptibility in La2 CuO4 studied by resonant inelastic x-ray scattering
Resonant inelastic X-ray scattering (RIXS) is a powerful probe of elementary
excitations in solids. It is now widely applied to study magnetic excitations.
However, its complex cross-section means that RIXS has been more difficult to
interpret than inelastic neutron scattering (INS). Here we report
high-resolution RIXS measurements of magnetic excitations of La2CuO4, the
antiferromagnetic parent of one system of high-temperature superconductors. At
high energies (~2 eV), the RIXS spectra show angular-dependent dd orbital
excitations which are found to be in good agreement with single-site multiplet
calculations. At lower energies (<0.3 eV), we show that the
wavevector-dependent RIXS intensities are proportional to the product of the
single-ion spin-flip cross section and the dynamical susceptibility of the
spin-wave excitations. When the spin-flip crosssection is dividing out, the
RIXS magnon intensities show a remarkable resemblance to INS data. Our results
show that RIXS is a quantitative probe the dynamical spin susceptibility in
cuprate and therefore should be used for quantitative investigation of other
correlated electron materials.Comment: 12 page
Correlation driven near-flat band Stoner excitations in a Kagome magnet
Among condensed matter systems, Mott insulators exhibit diverse properties
that emerge from electronic correlations. In itinerant metals, correlations are
usually weak, but can also be enhanced via geometrical confinement of
electrons, that manifest as `flat' dispersionless electronic bands. In the fast
developing field of topological materials, which includes Dirac and Weyl
semimetals, flat bands are one of the important components that can result in
unusual magnetic and transport behaviour. To date, characterisation of flat
bands and their magnetism is scarce, hindering the design of novel materials.
Here, we investigate the ferromagnetic Kagom\'{e} semimetal CoSnS
using resonant inelastic X-ray scattering. Remarkably, nearly non-dispersive
Stoner spin excitation peaks are observed, sharply contrasting with the
featureless Stoner continuum expected in conventional ferromagnetic metals. Our
band structure and dynamic spin susceptibility calculations, and thermal
evolution of the excitations, confirm the nearly non-dispersive Stoner
excitations as unique signatures of correlations and spin-polarized electronic
flat bands in CoSnS. These observations serve as a cornerstone for
further exploration of band-induced symmetry-breaking orders in topological
materials.Comment: 15 pages, 4 figures, and Supplementary Informatio
The nature of plasmon excitations in hole-doped cuprate superconductors
High Tc superconductors show a rich variety of phases associated with their
charge degrees of freedom. Valence charges can give rise to charge ordering or
acoustic plasmons in these layered cuprate superconductors. While charge
ordering has been observed for both hole- and electron-doped cuprates, acoustic
plasmons have only been found in electron-doped materials. Here, we use
resonant inelastic X-ray scattering (RIXS) to observe the presence of acoustic
plasmons in two families of hole-doped cuprate superconductors [La2-xSrxCuO4
(LSCO) and Bi2Sr1.6La0.4CuO6+d (Bi2201)], crucially completing the picture.
Interestingly, in contrast to the quasi-static charge ordering which manifests
at both Cu and O sites, the observed acoustic plasmons are predominantly
associated with the O sites, revealing a unique dichotomy in the behaviour of
valence charges in hole-doped cuprates.Comment: 11 pages, 7 figures + Supplementary Informatio
Recommended from our members
Parentsâ perspectives on their childrenâs music therapy: A synthesis of qualitative literature
There is no existing qualitative synthesis of the music therapy literature on parentsâ perspectives on their childrenâs music therapy. This study seeks to fill this gap, motivated by the first authorâs experiences as a clinician/researcher. A systematic search of health databases, hand searches of key journals and searches of doctoral theses were undertaken to identify relevant studies. Thirteen studies which met inclusion criteria, including a total of 102 participants, were identified. Relevant data were extracted from these studies for comparison and analysis, with quality of studies assessed using the CASP appraisal tool. Findings were analysed following procedures of thematic synthesis. Six descriptive themes were grouped into three analytic themes: Parents perceived positive impacts of music therapy on their children; parents experienced music therapy as a nurturing environment for themselves and their children; and some parents experienced challenges to their engagement with music therapy. Most studies (12/13) explored parentsâ perceptions of music therapy where they were included in sessions. The findings identify positive perceptions of family-centred models of music therapy for children and parents. Parentsâ perceptions of children were altered positively through experiencing them in new ways in music therapy. Parents also perceived positive outcomes for their children. These findings identify an emphasis in the qualitative literature on parentsâ perceptions on research into music therapy which includes parents in sessions. Only one study explored perceptions of a model where parents were not present during their childâs sessions. More research is needed into parentsâ perceptions of music therapy where parents are not present during sessions. Further intervention studies into family-centred models of music therapy with children are also recommended
Perceived quality of physiotherapist-led orthopaedic triage compared with standard practice in primary care: a randomised controlled trial
Recommended from our members
Physical and chemical impacts of a major storm on a temperate lake: a taste of things to come?
Extreme weather can have a substantial influence on lakes and is expected to become more frequent with climate change. We explored the influence of one particular extreme event, Storm Ophelia, on the physical and chemical environment of England's largest lake, Windermere. We found that the substantial influence of Ophelia on meteorological conditions at Windermere, in particular wind speed, resulted in a 25-fold increase (relative to the study-period average) in the wind energy flux at the lake-air interface. Following Ophelia, there was a short-lived mixing event in which the Schmidt stability decreased by over 100 Jm-2 and the thermocline deepened by over 10 m during a 12-hour period. As a result of changes to the strength of stratification, Ophelia also changed the internal seiche regime of Windermere with the dominant seiche period increasing from ~17 h pre-storm to ~21 h post-storm. Following Ophelia, there was an upwelling of cold and low-oxygenated waters at the southern-end of the lake. This had a substantial influence on the main outflow of Windermere, the River Leven, where dissolved oxygen concentrations decreased by ~48 %, from 9.3 mg L-1 to 4.8 mg L-1, while at the mid-lake monitoring station in Windermere, it decreased by only ~3%. This study illustrates that the response of a lake to extreme weather can cause important effects downstream, the influence of which may not be evident at the lake surface. To understand the impact of future extreme events fully, the whole lake and downstream-river system need to be studied together
Exchange of functional domains between a bacterial conjugative relaxase and the integrase of the human adeno-associated virus
Endonucleases of the HUH family are specialized in processing single-stranded DNA in a variety of evolutionarily highly conserved biological processes related to mobile genetic elements. They share a structurally defined catalytic domain for site-specific nicking and strand-transfer reactions, which is often linked to the activities of additional functional domains, contributing to their overall versatility. To assess if these HUH domains could be interchanged, we created a chimeric protein from two distantly related HUH endonucleases, containing the N-terminal HUH domain of the bacterial conjugative relaxase TrwC and the C-terminal DNA helicase domain of the human adeno-associated virus (AAV) replicase and site-specific integrase. The purified chimeric protein retained oligomerization properties and DNA helicase activities similar to Rep68, while its DNA binding specificity and cleaving-joining activity at oriT was similar to TrwC. Interestingly, the chimeric protein could catalyse site-specific integration in bacteria with an efficiency comparable to that of TrwC, while the HUH domain of TrwC alone was unable to catalyze this reaction, implying that the Rep68 C-terminal helicase domain is complementing the TrwC HUH domain to achieve site-specific integration into TrwC targets in bacteria. Our results illustrate how HUH domains could have acquired through evolution other domains in order to attain new roles, contributing to the functional flexibility observed in this protein superfamily.This work was supported by the Medical Research Council (MRC) grant MR/N022890/1 to EH and grant 1001764 to RML; National Institutes of Health (NIH) grant RO1-GM09285 to CRE; Spanish Ministry of Economy and competitiveness (MINECO) grant BIO2013-46414-P to ML and AFM is supported by a Doc.Mobility fellowship from the Swiss National Science Foundation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
- âŠ