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1.
J Clin Nurs ; 2024 Jun 04.
Artigo em Inglês | MEDLINE | ID: mdl-38837849

RESUMO

AIM: To pool existing studies to assess the overall effectiveness of integrated care for older adults (ICOPE)-based interventions in improving depressive symptoms in older adults. DESIGN: A systematic review and meta-analysis. DATA SOURCES: Ten databases were systematically searched from inception to 15 July 2023 and the search was last updated on 2 September 2023. METHODS: Standardized mean difference (SMD) was calculated using random effects models. RoB 2 and GRADEpro GDT were used to assess the methodological quality and confidence in the cumulative evidence. Funnel plots, egger's test and begg's test were used to analyse publication bias. Sensitivity, subgroup and meta-regression analyses were performed to explore potential sources of heterogeneity. RESULTS: The results of 18 studies showed ICOPE-based interventions had a significant effect on improving depressive symptoms (SMD = -.84; 95% CI, -1.20 to -.3647; p < .001; 18 RCTs, 5010 participants; very low-quality evidence). Subgroup analysis showed the intervention group was characterized by mean age (70-80 years old), intervention duration between 6 to 12 months, gender (female <50%), non-frail older adults, depressed older adults and mixed integration appeared to be more effective. Sensitivity analysis found the results to be robust. CONCLUSION: ICOPE-based interventions may be a potentially effective alternative approach to reduce depressive symptoms in the older adults. IMPLICATIONS FOR THE PROFESSION AND/OR PATIENT CARE: Healthcare professionals are expected to use ICOPE as one of the interventions for depressive symptoms in older adults, and this ICOPE could provide more comprehensive care services for older adults to reduce depressive symptoms. IMPACT: ICOPE-based interventions may be a potentially effective alternative approach to reduce depressive symptoms in the older adults. ICOPE-based interventions had a significant effect on reducing depressive symptoms in the older adults. The intervention group characterized by mean age of older adults, intervention duration, gender ratio, health condition and integration types may influence the effect size. REPORTING METHOD: According to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. PATIENT OR PUBLIC CONTRIBUTION: No Patient or Public Contribution.

2.
Int J Nurs Stud ; 154: 104755, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38522186

RESUMO

OBJECTIVE: The aims of this systematic review were to explore the pooled prevalence of multidimensional frailty assessed by the Tilburg Frailty Indicator among community-dwelling older adults. DESIGN: A systematic review and meta-analysis. METHODS: A comprehensive literature search was conducted across multiple databases, including PubMed, Web of Science, Embase, the Cochrane Library, CINAHL and three Chinese databases. Two independent researchers selected the literatures, extracted the data and evaluated the quality. All statistical analyses were performed using STATA version 16.0. RESULTS: There were 66 studies with a total of 40,597 individuals that were eligible for the meta-analysis. Data from the meta-analysis revealed the pooled prevalence of 42 % for multidimensional frailty (95 % CI: 38 %-45 %, I2 = 98.9 %, T2 = 0.024, p < 0.001). Among the six studies that provided data for different age groups, the results demonstrated an increasing trend in the prevalence of multidimensional frailty with advancing age. The results of gender-stratified analysis proved that the pooled prevalence of multidimensional frailty in women (45 %, 95 % CI: 39 %-51 %, p < 0.001) was higher than that in men (33 %, 95 % CI: 28 %-39 %, p < 0.001). Based on different education levels, the prevalence of multidimensional frailty is highest in the primary elementary or illiterate group (41 %, 95 % CI: 30 %-52 %, p < 0.001). According to different marital status types, the pooled prevalence of multidimensional frailty in the married group was significantly lower (36 %, 95 % CI: 28 %-43 %) than that in the unmarried, divorced or widowed group (51 %, 95 % CI: 37 %-65 %). CONCLUSIONS: Through a comprehensive review, we identified that 42 % of elderly individuals living in communities exhibit multidimensional frailty, indicating that multidimensional frailty is relatively common in this population. Stratified analysis revealed that advanced age, female gender, lower education level and unmarried status were associated with higher rates of multidimensional frailty.


Assuntos
Idoso Fragilizado , Fragilidade , Vida Independente , Humanos , Idoso , Prevalência , Fragilidade/epidemiologia , Idoso Fragilizado/estatística & dados numéricos , Idoso de 80 Anos ou mais , Masculino , Feminino
3.
Environ Sci Pollut Res Int ; 31(8): 11543-11558, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-38212564

RESUMO

Microplastics (MPs) have attracted much attention in recent years, due to the difficulty of degradation and threats to ecological systems and humans. Based on the analysis of 1429 articles on MPs in soil, we found that we know little about the behavior and fate of manure-born MPs from the livestock and poultry production systems to agriculture soils. This review summarizes the analytical methods for sampling, separation, and identification and the occurrence of MPs in livestock and poultry manure, mainly based on 7 surveys related to manure-born MPs. Then, the sources, fate, and environmental risks of MPs in livestock and poultry manure are discussed. MPs, heavy metals, pathogens, antibiotic resistance genes, and persistent organic pollutants are common pollutants in livestock and poultry manure. Worse, manure-born MPs will become smaller, rougher, and more numerous and could easily form more toxic compound pollution after complicated processes of manure treatment, which seriously threatens agricultural soil safety. Finally, an outlook is offered for future research. We hope this article to attract attention to the risks of MPs in livestock and poultry manure and provide a reference for future research.


Assuntos
Aves Domésticas , Solo , Humanos , Animais , Microplásticos , Plásticos , Gado , Esterco , Agricultura
4.
J Am Med Dir Assoc ; 24(11): 1637-1644.e8, 2023 11.
Artigo em Inglês | MEDLINE | ID: mdl-37660724

RESUMO

OBJECTIVE: To synthesize the pooled mortality risk estimate and determine whether cognitive frailty is a predictor of mortality. DESIGN: A systematic review and meta-analysis. SETTING AND PARTICIPANTS: The participants were community-dwelling older adults aged ≥60 years. METHODS: PubMed, Web of Science, Embase, CINAHL, and the Cochrane Library databases were systematically searched. Two researchers independently screened potentially eligible literature, evaluated the quality of the included studies, and then extracted the data. We used STATA, version 15.0 to perform the all data. RESULTS: Nineteen studies were included. The association between cognitive frailty and a higher risk of death was statistically significant [hazard ratio (HR), 2.01; 95% CI, 1.84-2.19; P < .001]. The outcomes indicated that cognitive frailty was a critical risk factor for predicting mortality (OR, 4.82; 95% CI, 1.59-14.57; P < .01). Based on different models of cognitive frailty, the results of subgroup analyses revealed that the risk of mortality was the highest in the Frail + mild cognitive impairment group (HR, 2.35; 95% CI, 2.05-2.70; P < .001). The subgroup analyses by region demonstrated that mortality risk was lowest in the European group (HR, 1.63; 95% CI, 1.4-1.87; P < .001). CONCLUSIONS AND IMPLICATIONS: This study quantitatively portrays the pooled mortality risk estimate of cognitive frailty. The results suggest that in older adults, cognitive frailty can be a predictor of mortality. The findings could alert health care providers to pay more attention to cognitive frailty.


Assuntos
Fragilidade , Mortalidade , Idoso , Humanos , Cognição , Idoso Fragilizado/psicologia , Fatores de Risco
5.
Aging Clin Exp Res ; 35(7): 1417-1428, 2023 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-37219756

RESUMO

BACKGROUND: With the aging of the population, frailty has attracted much attention, and the social dimension of frailty, namely social frailty, has also attracted attention. Studies have shown that social frailty can bring some adverse effects to the elderly, such as physical and cognitive function. AIMS: To explore the risk of adverse health outcomes in older adults with social frailty compared with older adults with non-social frailty. METHODS: Five databases were systematically searched from inception to February 28, 2023. Screening, data extraction and quality assessment were conducted independently by two researchers. The included studies were longitudinal studies of adverse outcomes in community-dwelling socially frail older adults, and the quality of each study was assessed using the Newcastle‒Ottawa Scale. RESULTS: A total of 15 studies were included based on the inclusion criteria, of which 4 were subjected to meta-analysis. The mean age of the included population ranged from 66.3 to 86.5 years. According to existing research, social frailty was predictive of some adverse outcomes, such as incident disability, depressive symptoms, and reduced neuropsychological function. The meta-analysis showed that social frailty had a significant predictive effect on mortality among older adults [HR = 2.27, (95% CI = 1.03-5.00)]. CONCLUSION: In community-dwelling older adults, social frailty was a predictor of mortality, incident disability, depressive symptoms and other adverse outcomes. Social frailty had a negative impact on older adults, so it was necessary to strengthen the screening of social frailty to reduce the incidence of adverse outcomes.


Assuntos
Pessoas com Deficiência , Fragilidade , Humanos , Idoso , Idoso de 80 Anos ou mais , Fragilidade/diagnóstico , Fragilidade/epidemiologia , Idoso Fragilizado , Vida Independente , Cognição
6.
Proc Natl Acad Sci U S A ; 120(2): e2215509119, 2023 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-36608295

RESUMO

Recently, Co-based honeycomb magnets have been proposed as promising candidate materials to host the Kitaev spin liquid (KSL) state. One of the front-runners is BaCo2(AsO4)2 (BCAO), where it was suggested that the exchange processes between Co2+ ions via the surrounding edge-sharing oxygen octahedra could give rise to bond-dependent Kitaev interactions. In this work, we present and analyze a comprehensive inelastic neutron scattering (INS) study of BCAO with fields in the honeycomb plane. Combining the constraints from the magnon excitations in the high-field polarized state and the inelastic spin structure factor measured in zero magnetic field, we examine two leading theoretical models: the Kitaev-type [Formula: see text] model and the XXZ[Formula: see text]model. We show that the existing experimental data can be consistently accounted for by the XXZ[Formula: see text]model but not by the [Formula: see text] model, and we discuss the implications of these results for the realization of a spin liquid phase in BCAO and more generally for the realization of the Kitaev model in cobaltates.

7.
Age Ageing ; 51(12)2022 12 05.
Artigo em Inglês | MEDLINE | ID: mdl-36571775

RESUMO

BACKGROUND: interventions targeting older adults with cognitive frailty have grown rapidly in recent years with inconsistent findings. However, there is no meta-analysis that has synthesised pooled estimates. OBJECTIVE: to synthesise the pooled effect of current targeted interventions in older people with cognitive frailty. METHODS: we conducted a systematic search in PubMed, Embase, Web of Science, the Cochrane Library, the JBI database and three Chinese databases (CNKI, Wan-Fang and VIP) for literature from the inception of the database until 8 March 2022. The mean difference or standardised mean difference with 95% CIs was calculated. The methodological quality was assessed by the Cochrane RoB 2.0. The certainty of evidence was assessed using the GRADE criteria. RESULTS: thirteen randomised controlled trials with a total of 1,089 participants were included. The results of the meta-analysis showed that older adults with cognitive frailty in the intervention groups had significant improvement in frailty score [MD = -1.67, 95% CI (-2.39, -0.95), P < 0.00001, I2 = 97%], global cognitive function [MD = 3.38, 95% CI (1.90, 4.85), P < 0.00001, I2 = 93%], mobility [MD = -0.96, 95% CI (-1.27, -1.66), P < 0.00001, I2 = 0%], muscle strength [SMD = 0.75, 95% CI (0.09, 1.41), P = 0.03, I2 = 85%] and nutritional status [MNA:MD = 5.64, 95% CI (3.99, 7.29), P < 0.00001, I2 = 89%; ALB: MD = 3.23, 95% CI (0.76, 5.71), P = 0.01, I2 = 93%; PALB: MD = 54.52, 95% CI (25.26, 83.77), P = 0.0003, I2 = 96%; TRF: MD = 0.64, 95% CI (0.22, 1.06), P = 0.003, I2 = 97%]. The overall certainty of the evidence ranged from low to moderate. CONCLUSIONS: interventions targeting older adults with cognitive frailty are effective in improving physical frailty, global cognitive function, physical function and nutritional status with low to moderate certainty. More research is still needed in the future to further enrich the evidence in these fields. PROSPERO NUMBER: CRD42022318758.


Assuntos
Fragilidade , Humanos , Idoso , Fragilidade/diagnóstico , Fragilidade/terapia , Cognição , Ensaios Clínicos Controlados Aleatórios como Assunto
8.
Nat Commun ; 13(1): 3073, 2022 Jun 02.
Artigo em Inglês | MEDLINE | ID: mdl-35654798

RESUMO

Quantum phase transitions in quantum matter occur at zero temperature between distinct ground states by tuning a nonthermal control parameter. Often, they can be accurately described within the Landau theory of phase transitions, similarly to conventional thermal phase transitions. However, this picture can break down under certain circumstances. Here, we present a comprehensive study of the effect of hydrostatic pressure on the magnetic structure and spin dynamics of the spin-1/2 ladder compound C9H18N2CuBr4. Single-crystal heat capacity and neutron diffraction measurements reveal that the Néel-ordered phase breaks down beyond a critical pressure of Pc ∼ 1.0 GPa through a continuous quantum phase transition. Estimates of the critical exponents suggest that this transition may fall outside the traditional Landau paradigm. The inelastic neutron scattering spectra at 1.3 GPa are characterized by two well-separated gapped modes, including one continuum-like and another resolution-limited excitation in distinct scattering channels, which further indicates an exotic quantum-disordered phase above Pc.

10.
J Adv Nurs ; 78(3): 709-721, 2022 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-34617618

RESUMO

AIMS: To systematically search for clinical practice guidelines focusing on the prevention and management of frailty, to evaluate their methodological quality and to synthesize the consensus recommendations. DESIGN: A systematic review. DATA SOURCES: Guideline websites, related professional association websites and electronic databases were systematically searched through 4 November 2020. REVIEW METHODS: We evaluated the methodological quality of the eligible guidelines using the Appraisal of Guidelines Research and Evaluation II (AGREE II). Two reviewers synthesized the consensus recommendations proposed by at least two guidelines. RESULTS: Eight guidelines met the eligibility criteria and were included in the review. The mean scores of the six domains were as follows: the 'scope and purpose' domain scored 88.0%, the 'clarity of presentation' domain scored 81.9%, the 'stakeholder involvement' domain scored 63.4%, the 'editorial independence' domain scored 62.2%, the 'rigour of development' domain scored 61.1% and the 'applicability' domain scored 57.8%. In total, we synthesized 23 recommendations for the prevention and management of frailty that are consistent among the included guidelines. CONCLUSIONS: The number of clinical practice guidelines for the prevention and management of frailty is limited. The methodological quality of existing guidelines needs to be improved. Our synthesized findings provide an intuitive, convenient and summative reference resource for frailty prevention and management. It' is worth noting that recommendations described in the included guidelines require additional detail. IMPACT: Although the prevention and management of frailty is urgent, there is currently a lack of evidences guiding these processes, especially in the prevention. The methodological quality of existing guidelines is insufficient, and the recommendations described in the guidelines require additional detail. Therefore, users of these guidelines, especially nurses, should make a careful decision according to the specific situation when using. Nurses also have a key role in providing more clinical evidences for the improvement of the quality of the guidelines.


Assuntos
Fragilidade , Medicina Baseada em Evidências , Fragilidade/prevenção & controle , Humanos
11.
Int J Nurs Stud ; 125: 104112, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34758429

RESUMO

OBJECTIVE: The aim of this systematic review and meta-analysis was to investigate the pooled prevalence of cognitive frailty among community-dwelling older adults and provide evidence-based support for policy-makers planning health and social care policies. DESIGN: A systematic review and meta-analysis. METHODS: PubMed, Web of Science, Embase and the Cochrane Library were systematically searched from their inception to December 10, 2020. Descriptive studies (cross-sectional studies or population-based longitudinal studies) and cohort studies were available. Participants were community-dwelling older adults aged 60 years and above. Two researchers independently screened the literature, extracted the data and evaluated the quality of the included studies. All statistical analyses were conducted using Stata 15.0. RESULTS: We screened 2815 records, among which 24 studies met the inclusion criteria and were included in the review. The pooled prevalence of cognitive frailty was 9% (95% CI: 8%-11%, I2 = 99.3%). The results of the subgroup analysis showed that the pooled prevalence of cognitive frailty was 11% (95% CI: 9%-14%) in men and 15% (95% CI: 11%-19%) in women. The pooled prevalence of cognitive frailty based on the descriptive studies and cohort studies was 7% (95% CI: 5%-9%) and 17% (95% CI: 11%-22%), respectively. The pooled estimates of cognitive frailty prevalence were 6% (95% CI: 4%-8%) from 2012 to 2017 and 11% (95% CI: 9%-14%) from 2018 to 2020. CONCLUSIONS: This systematic review analyzed the available literature and revealed that the pooled prevalence of cognitive frailty among community-dwelling older adults was 9%. The stratified analysis showed that the prevalence of cognitive frailty was higher in older women. In addition, the prevalence has increased in recent years, which has important implications for adapting health and social care systems.


Assuntos
Fragilidade , Idoso , Cognição , Estudos Transversais , Feminino , Idoso Fragilizado , Humanos , Vida Independente , Masculino , Prevalência
12.
Phys Rev Lett ; 127(1): 017201, 2021 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-34270292

RESUMO

Sr_{2}CuTe_{0.5}W_{0.5}O_{6} is a square-lattice magnet with superexchange between S=1/2Cu^{2+} spins mediated by randomly distributed Te and W ions. Here, using sub-K temperature and 20 µeV energy resolution neutron scattering experiments we show that this system transits from a gapless disorder-induced spin liquid to a new quantum state below T_{f}=1.7(1) K, exhibiting a weak frozen moment of ⟨S⟩/S∼0.1 and low energy dynamic susceptibility, χ^{''}(ℏω), linear in energy which is surprising for such a weak freezing in this highly fluctuating quantum regime.

13.
Sci Adv ; 7(25)2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-34134975

RESUMO

Ferromagnetically interacting Ising spins on the pyrochlore lattice of corner-sharing tetrahedra form a highly degenerate manifold of low-energy states. A spin flip relative to this "spin-ice" manifold can fractionalize into two oppositely charged magnetic monopoles with effective Coulomb interactions. To understand this process, we have probed the low-temperature magnetic response of spin ice to time-varying magnetic fields through stroboscopic neutron scattering and SQUID magnetometry on a new class of ultrapure Ho2Ti2O7 crystals. Covering almost 10 decades of time scales with atomic-scale spatial resolution, the experiments resolve apparent discrepancies between prior measurements on more disordered crystals and reveal a thermal crossover between distinct relaxation processes. Magnetic relaxation at low temperatures is associated with monopole motion through the spin-ice vacuum, while at elevated temperatures, relaxation occurs through reorientation of increasingly spin-like monopolar bound states. Spin fractionalization is thus directly manifest in the relaxation dynamics of spin ice.

14.
Sci Adv ; 7(21)2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-34138738

RESUMO

The observation of quantum criticality in diverse classes of strongly correlated electron systems has been instrumental in establishing ordering principles, discovering new phases, and identifying the relevant degrees of freedom and interactions. At focus so far have been insulators and metals. Semimetals, which are of great current interest as candidate phases with nontrivial topology, are much less explored in experiments. Here, we study the Kondo semimetal CeRu4Sn6 by magnetic susceptibility, specific heat, and inelastic neutron scattering experiments. The power-law divergence of the magnetic Grünesien ratio reveals that, unexpectedly, this compound is quantum critical without tuning. The dynamical energy over temperature scaling in the neutron response throughout the Brillouin zone and the temperature dependence of the static uniform susceptibility, indicate that temperature is the only energy scale in the criticality. Such behavior, which has been associated with Kondo destruction quantum criticality in metallic systems, could be generic in the semimetal setting.

15.
Mol Med Rep ; 23(3)2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-33398368

RESUMO

Radiation therapy, one of the major treatment options for cancer, can cause delayed heart damage. The circular RNA (circRNA) circFOXO3 (hsa_circ_0006404) is associated with cancer progression. However, the functions of circFOXO3 in radiation­induced cardiotoxicity remains unknown. The present study aimed to identify the functions of cirFOXO3 in radiation­induced cardiotoxicity. The present study established circFOXO3­knockdown (KD) or ­overexpressing (OE) cardiomyocytes. Functional assay results showed that KD of circFOXO3 in cardiomyocytes significantly increased DNA damage and apoptosis after radiation. By contrast, OE of circFOXO3 reduced DNA damage and apoptosis rates in response to radiation. Mechanistically, KD of circFOXO3 elevated the levels of Bax, caspase 3 and caspase 7, and decreased Bcl­2 expression, whereas OE of circFOXO3 decreased Bax, caspase 3 and caspase 7 expression, and increased Bcl­2 expression. Thus, the present study indicated that circFOXO3 protected cardiomyocytes from radiation­induced cardiotoxicity by reducing DNA damage and apoptosis. circFOXO3 may be a potential therapeutic target against radiation­induced cardiotoxicity.


Assuntos
Apoptose , Cardiotoxicidade/metabolismo , Dano ao DNA , Raios gama/efeitos adversos , Miócitos Cardíacos/metabolismo , RNA Circular/metabolismo , Lesões Experimentais por Radiação/metabolismo , Animais , Proteínas Reguladoras de Apoptose/metabolismo , Cardiotoxicidade/genética , Cardiotoxicidade/patologia , Linhagem Celular , Humanos , Miócitos Cardíacos/patologia , Lesões Experimentais por Radiação/patologia
16.
Artigo em Inglês | MEDLINE | ID: mdl-37964898

RESUMO

Magnetic fluctuations is the leading candidate for pairing in cuprate, iron-based, and heavy fermion superconductors. This view is challenged by the recent discovery of nodeless superconductivity in CeCu2Si2, and calls for a detailed understanding of the corresponding magnetic fluctuations. Here, we mapped out the magnetic excitations in superconducting (S-type) CeCu2Si2 using inelastic neutron scattering, finding a strongly asymmetric dispersion for E≲1.5meV, which at higher energies evolves into broad columnar magnetic excitations that extend to E≳5meV. While low-energy magnetic excitations exhibit marked three-dimensional characteristics, the high-energy magnetic excitations in CeCu2Si2 are almost two-dimensional, reminiscent of paramagnons found in cuprate and iron-based superconductors. By comparing our experimental findings with calculations in the random-phase approximation,we find that the magnetic excitations in CeCu2Si2 arise from quasiparticles associated with its heavy electron band, which are also responsible for superconductivity. Our results provide a basis for understanding magnetism and superconductivity in CeCu2Si2, and demonstrate the utility of neutron scattering in probing band renormalization in heavy fermion metals.

17.
Nat Commun ; 11(1): 6003, 2020 Nov 26.
Artigo em Inglês | MEDLINE | ID: mdl-33243978

RESUMO

Nickelates are a rich class of materials, ranging from insulating magnets to superconductors. But for stoichiometric materials, insulating behavior is the norm, as for most late transition metal oxides. Notable exceptions are the 3D perovskite LaNiO3, an unconventional paramagnetic metal, and the layered Ruddlesden-Popper phases R4Ni3O10, (R = La, Pr, Nd). The latter are particularly intriguing because they exhibit an unusual metal-to-metal transition. Here, we demonstrate that this transition results from an incommensurate density wave with both charge and magnetic character that lies closer in its behavior to the metallic density wave seen in chromium metal than the insulating stripes typically found in single-layer nickelates like La2-xSrxNiO4. We identify these intertwined density waves as being Fermi surface-driven, revealing a novel ordering mechanism in this nickelate that reflects a coupling among charge, spin, and lattice degrees of freedom that differs not only from the single-layer materials, but from the 3D perovskites as well.

18.
Phys Rev B ; 1012020.
Artigo em Inglês | MEDLINE | ID: mdl-33655091

RESUMO

We report a comprehensive neutron scattering study of low energy magnetic excitations in the breathing pyrochlore helimagnetic Cu2OSeO3. Fully documenting the four lowest energy magnetic modes that leave the ferrimagnetic configuration of the "strong tetrahedra" intact ( | ℏ ω | < 13 meV), we find gapless quadratic dispersion at the point for energies above 0.2 meV, two doublets separated by 1.6(2) meV at the R point, and a bounded continuum at the X point. Our constrained rigid spin cluster model relates these features to Dzyaloshinskii-Moriya (DM) interactions and the incommensurate helical ground state. Combining conventional spin wave theory with a spin cluster form factor accurately reproduces the measured equal time structure factor through multiple Brillouin zones. An effective spin Hamiltonian describing complex anisotropic intercluster interactions is obtained.

19.
Phys Rev B ; 101(14)2020.
Artigo em Inglês | MEDLINE | ID: mdl-33655092

RESUMO

We use inelastic neutron scattering to study the effect of a magnetic field on the neutron spin resonance (E r = 3.6 meV) of superconducting FeSe (T c = 9 K). While a field aligned along the in-plane direction broadens and suppresses the resonance, a c-axis aligned field does so much more efficiently, consistent with the anisotropic field-induced suppression of the superfluid density from the heat capacity measurements. These results suggest that the resonance in FeSe is associated with the superconducting electrons arising from orbital selective quasiparticle excitations between the hole and electron Fermi surfaces.

20.
Nat Mater ; 18(7): 709-716, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-31110345

RESUMO

Superconductivity in FeSe emerges from a nematic phase that breaks four-fold rotational symmetry in the iron plane. This phase may arise from orbital ordering, spin fluctuations or hidden magnetic quadrupolar order. Here we use inelastic neutron scattering on a mosaic of single crystals of FeSe, detwinned by mounting on a BaFe2As2 substrate to demonstrate that spin excitations are most intense at the antiferromagnetic wave vectors QAF = (±1, 0) at low energies E = 6-11 meV in the normal state. This two-fold (C2) anisotropy is reduced at lower energies, 3-5 meV, indicating a gapped four-fold (C4) mode. In the superconducting state, however, the strong nematic anisotropy is again reflected in the spin resonance (E = 3.6 meV) at QAF with incommensurate scattering around 5-6 meV. Our results highlight the extreme electronic anisotropy of the nematic phase of FeSe and are consistent with a highly anisotropic superconducting gap driven by spin fluctuations.

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