In this work, we show that the zero field excitation spectra in the quantum spin ice candidate pyrochlore compound Yb2Ti2O7 is a continuum characterized by a very broad and almost flat dynamical response which extends up to 1 − 1.5 meV, coexisting or not with a quasi-elastic response depending on the wave-vector. The spectra do not evolve between 50 mK and 2 K, indicating that the spin dynamics is only little affected by the temperature in both the short-range correlated and ordered regimes. Although classical spin dynamics simulations qualitatively capture some of the experimental observations, we show that they fail to reproduce this broad continuum. In particular, the simulations predict an energy scale twice smaller than the experimental observations. This analysis is based on a careful determination of the exchange couplings, able to reproduce both the zero field diffuse scattering and the spin wave spectrum rising in the field polarized state. According to this analysis, Yb2Ti2O7 lies at the border between a ferro and an antiferromagnetic phase. These results suggest that the unconventional ground state of Yb2Ti2O7 is governed by strong quantum fluctuations arising from the competition between those phases. The observed spectra may correspond to a continuum of deconfined spinons as expected in quantum spin liquids. arXiv:1506.01729v1 [cond-mat.str-el]

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(2016) Antiferroquadrupolar correlations in the quantum spin ice candidate Pr2Zr2O7. Physical Review B, 94 (16). 165153 Permanent WRAP URL: http://wrap.warwick.ac.uk/87826 Copyright and reuse:The Warwick Research Archive Portal (WRAP) makes this work by researchers of the University of Warwick available open access under the following conditions. Copyright © and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable the material made available in WRAP has been checked for eligibility before being made available.Copies of full items can be used for personal research or study, educational, or not-for-profit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. Publisher statement: © 2016 American Physical Society A note on versions:The version presented here may differ from the published version or, version of record, if you wish to cite this item you are advised to consult the publisher's version. Please see the 'permanent WRAP URL' above for details on accessing the published version and note that access may require a subscription. We present an experimental study of the quantum spin ice candidate pyrochlore compound Pr 2 Zr 2 O 7 by means of magnetization measurements, specific heat, and neutron scattering up to 12 T and down to 60 mK. When the field is applied along the [111] and [110] directions, k = 0 field-induced structures settle in. We find that the ordered moment rises slowly, even at very low temperature, in agreement with macroscopic magnetization. Interestingly, for H [110], the ordered moment appears on the so-called α chains only. The spin excitation spectrum is essentially inelastic and consists in a broad flat mode centered at about 0.4 meV with a magnetic structure factor which resembles the spin ice pattern. For H [110] (at least up to 2.5 T), we find that a well-defined mode forms from this broad response, whose energy increases with H , in the same way as the temperature of the specific-heat anomaly. We finally discuss these results in the light of mean field calculations and propose an interpretation where quadrupolar interactions play a major role, overcoming the magnetic exchange. In this picture, the spin ice pattern appears shifted up to finite energy because of those interactions. We then propose a range of acceptable parameters for Pr 2 Zr 2 O 7 that allow to reproduce several experimental features observed under field. With these parameters, the actual ground state of this material would be an antiferroquadrupolar liquid with spin-ice-like excitations.

The dynamical magnetic correlations in Tb2Ti2O7 have been investigated using polarized inelastic neutron scattering. Dispersive excitations are observed, emerging from pinch points in reciprocal space and characterized by an anisotropic spectral weight. Anomalies in the crystal field and phonon excitation spectrum at Brillouin zone centers are also reported. These findings suggest that Coulomb phases, although they present a disordered ground state with dipolar correlations, allow the propagation of collective excitations. They also point out a strong spin-lattice coupling, which likely drives effective interactions between the 4f quadrupolar moments.

The nature of the unconventional ordered phase occurring in CeRu2Al10 below T0 = 27 K was investigated by neutron scattering. Powder diffraction patterns show clear superstructure peaks corresponding to forbidden (h + k)-odd reflections of the Cmcm space group. Inelastic neutron scattering experiments further reveal a pronounced magnetic excitation developing in the ordered phase at an energy of 8 meV.

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BackgroundCurrent asthma management guidelines are based on the level of asthma control. The impact of asthma control on health care resources and quality of life (QoL) is insufficiently studied. EUCOAST study was designed to describe costs and QoL in adult patients according to level of asthma control in France and Spain.MethodsAn observational cost of illness study was conducted simultaneously in both countries among patients age greater or equal to 18 with a diagnosis of asthma for at least 12 months. Patients were recruited prospectively by GPs in 2010 in four waves to avoid a seasonal bias. Health care resources utilization of the three months before the inclusion was collected through physician questionnaires. Asthma control was evaluated using 2009 GINA criteria over a 3-month period. QoL was assessed using EQ-5D-3L®.Results2,671 patients (France: 1,154; Spain: 1,517) were enrolled. Asthma was controlled in 40.6% [95% CI: 37.7% - 43.4%] and 29.9% [95% CI: 27.6% - 32.3%] of French and Spanish patients respectively.For all types of costs, the percentage of patients using health care resources varied significantly according to the level of asthma control. The average cost (euros/3-months/patient) of controlled asthma was €85.4 (SD: 153.5) in France compared with €314.0 (SD: 2,160.4) for partially controlled asthma and €537.9 (SD: 2,355.7) for uncontrolled asthma (p<0.0001). In Spain, the corresponding figures were €152.6 (SD: 162.1), €241.2 (SD: 266.8), and €556.8 (SD: 762.4). EQ-5D-3L® score was higher (p<0.0001) in patients with controlled asthma compared to partially controlled and uncontrolled asthma in both countries (respectively 0.88; 0.78; 0.63 in France and 0.89; 0.82; 0.69 in Spain).ConclusionsIn both countries, patients presenting with uncontrolled asthma had a significantly higher asthma costs and lower scores of Qol compared to the others.