1,683 research outputs found
Spectrum of a magnetized strong-leg quantum spin ladder
Inelastic neutron scattering is used to measure the spin excitation spectrum
of the Heisenberg ladder material (CHN)CuBr in its
entirety, both in the gapped spin-liquid and the magnetic field induced
Tomonaga-Luttinger spin liquid regimes. A fundamental change of the spin
dynamics is observed between these two regimes. DMRG calculations
quantitatively reproduce and help understand the observed commensurate and
incommensurate excitations. The results validate long-standing quantum field
theoretical predictions, but also test the limits of that approach
On a self-sustained process at large scale in the turbulent channel flow
Large-scale motions, important in turbulent shear flows, are frequently
attributed to the interaction of structures at smaller scale. Here we show
that, in a turbulent channel at Re_{\tau} \approx 550, large-scale motions can
self-sustain even when smaller-scale structures populating the near-wall and
logarithmic regions are artificially quenched. This large-scale self-sustained
mechanism is not active in periodic boxes of width smaller than Lz ~ 1.5h or
length shorter than Lx ~ 3h which correspond well to the most energetic large
scales observed in the turbulent channel
Excitations in the quantum paramagnetic phase of the quasi-one-dimensional Ising magnet CoNbO in a transverse field: Geometric frustration and quantum renormalization effects
The quasi-one-dimensional (1D) Ising ferromagnet CoNbO has recently
been driven via applied transverse magnetic fields through a continuous quantum
phase transition from spontaneous magnetic order to a quantum paramagnet, and
dramatic changes were observed in the spin dynamics, characteristic of weakly
perturbed 1D Ising quantum criticality. We report here extensive single-crystal
inelastic neutron scattering measurements of the magnetic excitations
throughout the three-dimensional (3D) Brillouin zone in the quantum
paramagnetic phase just above the critical field to characterize the effects of
the finite interchain couplings. In this phase, we observe that excitations
have a sharp, resolution-limited line shape at low energies and over most of
the dispersion bandwidth, as expected for spin-flip quasiparticles. We map the
full bandwidth along the strongly dispersive chain direction and resolve clear
modulations of the dispersions in the plane normal to the chains,
characteristic of frustrated interchain couplings in an antiferromagnetic
isosceles triangular lattice. The dispersions can be well parametrized using a
linear spin-wave model that includes interchain couplings and further neighbor
exchanges. The observed dispersion bandwidth along the chain direction is
smaller than that predicted by a linear spin-wave model using exchange values
determined at zero field, and this effect is attributed to quantum
renormalization of the dispersion beyond the spin-wave approximation in fields
slightly above the critical field, where quantum fluctuations are still
significant.Comment: 11 pages, 6 figures. Updated references. Minor changes to text and
figure
Influence of static Jahn-Teller distortion on the magnetic excitation spectrum of PrO2: A synchrotron x-ray and neutron inelastic scattering study
A synchrotron x-ray diffraction study of the crystallographic structure of
PrO2 in the Jahn-Teller distorted phase is reported. The distortion of the
oxygen sublattice, which was previously ambiguous, is shown to be a chiral
structure in which neighbouring oxygen chains have opposite chiralities. A
temperature dependent study of the magnetic excitation spectrum, probed by
neutron inelastic scattering, is also reported. Changes in the energies and
relative intensities of the crystal field transitions provide an insight into
the interplay between the static and dynamic Jahn-Teller effects.Comment: 7 pages, 6 figure
Inelastic neutron scattering studies of Crystal Field Levels in PrOsAs
We use neutron scattering to study the Pr crystalline electric field
(CEF) excitations in the filled skutterudite PrOsAs. By comparing
the observed levels and their strengths under neutron excitation with the
theoretical spectrum and neutron excitation intensities, we identify the
Pr CEF levels, and show that the ground state is a magnetic
triplet, and the excited states ,
and are at 0.4, 13 and 23 meV, respectively. A comparison of the
observed CEF levels in PrOsAs with the heavy fermion superconductor
PrOsSb reveals the microscopic origin of the differences in the
ground states of these two filled skutterudites.Comment: 7 pages, 7 figure
Belief heterogeneity and survival in incomplete markets
In complete markets economies (Sandroni [16]), or in economies with Pareto optimal outcomes (Blume and Easley [10]), the market selection hypothesis holds, as long as traders have identical discount factors. Traders who survive must have beliefs that merge with the truth. We show that in incomplete markets, regardless of tradersâ discount factors, the market selects for a range of beliefs, at least some of which do not merge with the truth. We also show that impatient traders with incorrect beliefs can survive and that these incorrect beliefs impact prices. These beliefs may be chosen so that they are far from the truth
Social Preferences, Skill Segregation and Wage Dynamics
We study the earning structure and the equilibrium asignment of workers to firms in a model in which workers have social preferences, and skills are perfectly substitutable in production. Firms offer long-term contracts, and we allow for frictions in the labour market in the form of mobility costs. The model delivers specific predictions about the nature of worker flows, about the characteristic of workplace skill segregation, and about wage dispersion both within and cross firms. We shows that long-term contracts in the resence of social preferences associate within-firm wage dispersion with novel "internal labour market" features such as gradual promotions, productivity-unrelated wage increases, and downward wage flexibility. These three dynamic features lead to productivity-unrelated wage volatily within firms.Publicad
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