974 research outputs found
Unusual interplay between copper-spin and vortex dynamics in slightly overdoped La{1.83}Sr{0.17}CuO{4}
Our inelastic neutron scattering experiments of the spin excitations in the
slightly overdoped La{1.83}Sr{0.17}CuO{4} compound show that, under the
application of a magnetic field of 5 Tesla, the low-temperature susceptibility
undergoes a weight redistribution centered at the spin-gap energy. Furthermore,
by comparing the temperature dependence of the neutron data with
ac-susceptibility and magnetization measurements, we conclude that the filling
in of the spin gap tracks the irreversibility/melting temperature rather than
Tc2, which indicates an unusual interplay between the magnetic vortices and the
spin excitations even in the slightly overdoped regime of high-temperature
superconductors.Comment: 7 pages, including 5 figure
Influence of higher d-wave gap harmonics on the dynamical magnetic susceptibility of high-temperature superconductors
Using a fermiology approach to the computation of the magnetic susceptibility
measured by neutron scattering in hole-doped high-Tc superconductors, we
estimate the effects on the incommensurate peaks caused by higher d-wave
harmonics of the superconducting order parameter induced by underdoping. The
input parameters for the Fermi surface and d-wave gap are taken directly from
angle resolved photoemission (ARPES) experiments on Bi{2}Sr{2}CaCu{2}O{8+x}
(Bi2212). We find that higher d-wave harmonics lower the momentum dependent
spin gap at the incommensurate peaks as measured by the lowest spectral edge of
the imaginary part in the frequency dependence of the magnetic susceptibility
of Bi2212. This effect is robust whenever the fermiology approach captures the
physics of high-Tc superconductors. At energies above the resonance we observe
diagonal incommensurate peaks. We show that the crossover from parallel
incommensuration below the resonance energy to diagonal incommensuration above
it is connected to the values and the degeneracies of the minima of the
2-particle energy continuum.Comment: 13 pages, 7 figure
Doping dependence of the vortex glass and sublimation transitions in the high- superconductor LaSrCuO as determined from macroscopic measurements
Magnetization and ac-susceptibility measurements are used to characterize the
mixed phase of the high-temperature cuprate superconductor
LaSrCuO over a large range of doping (0.075
0.20). The first order vortex lattice phase transition line , the
upper critical field and the second peak have been
investigated up to high magnetic fields (8 Tesla applied perpendicular to the
planes). Our results reveal a strong doping dependence of the magnetic
phase diagram, which can mainly be explained by the increasing anisotropy with
underdoping. Within our interpretation, the first order vortex lattice phase
transition is due to the sublimation (rather than melting) of the vortex
lattice into a gas of pancake vortices, whereas the second peak is related to
the transition to a more disordered vortex glass state.Comment: 7 pages, 5 figure
LHCb Conditions Database
The LHCb Conditions Database (CondDB) project aims to provide the necessary tools to handle non-event time-varying data. The LCG project COOL provides a generic API to handle this type of data and an interface to it has been integrated into the LHCb framework Gaudi. The interface is based on the Persistency Service infrastructure of Gaudi, allowing the user to load it at run-time only if needed. Since condition data are varying with time, as the events are processed, condition objects in memory must be kept synchronized to the values in the database for the current event time. A specialized service has been developed independently of the COOL API interface to provide an automated and optimized update of the condition objects in memory. The High Level Trigger of LHCb is a specialized version of an LHCb reconstruction/analysis program and as such it will need conditions, like alignments and calibrations, from the conditions database. For performance reasons, the HLT processes running on the Event Filter Farm cannot access the database directly. A special Online implementation of the CondDB service is thus needed under supervision of the LHCb Control system
A small angle neutron scattering study of the vortex matter in La{2-x}Sr{x}CuO{4} (x=0.17)
The magnetic phase diagram of slightly overdoped La{2-x}Sr{x}CuO{4} (x=0.17)
is characterised by a field-induced hexagonal to square transition of the
vortex lattice at low fields (~0.4 Tesla) [R. Gilardi et al., Phys. Rev. Lett.
88, 217003 (2002)]. Here we report on a small angle neutron scattering study of
the vortex lattice at higher fields, that reveals no further change of the
coordination of the square vortex lattice up to 10.5 Tesla applied
perpendicular to the CuO2 planes. Moreover, it is found that the diffraction
signal disappears at temperatures well below Tc, due to the melting of the
vortex lattice.Comment: 3 pages, 2 figures. Presented at the New3SC-4 meeting, San Diego,
Jan. 16-21 2003; to be published in Int. J. Mod. Phys.
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