235 research outputs found
Non-immunological hydrops fetalis
A case of hydrops fetalis which was not due to isoimmunization is presented. The condition was diagnosed antenatally by means of Ultrasonography and the infant was delivered at 32 weeks' gestation. He required intensive care, but survived and is well at 18 months of age. The causation, diagnosis and management of this problem are discussed
Incomplete Protection of the Surface Weyl Cones of the Kondo Insulator SmB: Spin Exciton Scattering
The compound SmB is a Kondo Insulator, where the lowest-energy bulk
electronic excitations are spin excitons. It also has surface states that are
subjected to strong spin-orbit coupling. It has been suggested that SmB is
also a topological insulator. Here we show that, despite the absence of
time-reversal symmetry breaking and the presence of strong spin-orbit coupling,
the chiral spin texture of the Weyl cone is not completely protected. In
particular, we show that the spin-exciton mediated scattering produces features
in the surface electronic spectrum at energies separated from the surface Fermi
energy by the spin-exciton energy. Despite the features being far removed from
the surface Fermi energy, they are extremely temperature dependent. The
temperature variation occurs over a characteristic scale determined by the
dispersion of the spin exciton. The structures may be observed by electron
spectroscopy at low temperatures.Comment: 7 pages, 5 figure
Magnetic transitions induced by pressure and magnetic field in a two-orbital -electron model in cubic and tetragonal lattices
We investigate the onset and evolution of under the simultaneous application
of pressure and magnetic field of distinct itinerant N\'eel states using the
underscreened Anderson Lattice Model (UALM) which has been proposed to describe
-electron systems. The model is composed by two narrow -bands (of either
or character) that hybridize with a wide -band and local
-electron interactions. We consider both cubic and tetragonal lattices. The
N\'eel order parameters and are assumed to be
fixed by an Ising anisotropy. The applied magnetic field is parallel to
the anisotropy axis. It has been assumed that the variation of the band width
is sensitive to pressure. In the absence of a magnetic field, the increase
of takes the system from the phase AF to another phase AF. The
phase AF occurs when while in the AF
phase the gaps satisfy . In the presence of a
magnetic field , the phase AF is quickly suppressed and reappears
again at intermediate values of the magnetic field while it is predominant at
higher magnetic fields. The analysis of the partial density of states close to
the phase transition between the phases AF and AF, allows a better
understanding the mechanism responsible whereby the transition is induced by an
increase in the magnetic field. As a important general result, we found that
the magnetic field favours the phase AF while the phase AF is
suppressed. For the tetragonal lattice, the phase AF is even more favored
when and increases concomitantly, where and are the lattice
parameters
Crystalline Electric Field Effects in CeMIn5: Superconductivity and the Influence of Kondo Spin Fluctuations
We have measured the crystalline electric field (CEF) excitations of the
CeMIn5 (M = Co, Rh, Ir) series of heavy fermion superconductors by means of
inelastic neutron scattering. Fits to a CEF model reproduce the inelastic
neutron scattering spectra and the high temperature magnetic susceptibility.
The CEF parameters, energy level splittings, and wavefunctions are tabulated
for each member of the CeMIn5 series and compared to each other as well as to
the results of previous measurements. Our results indicate that the CEF level
splitting in all three materials is similar, and can be thought of as being
derived from the cubic parent compound CeIn3 in which an excited state quartet
at ~12 meV is split into two doublets by the lower symmetry of the tetragonal
environment of the CeMIn5 materials. In each case, the CEF excitations are
observed as broad lines in the inelastic neutron scattering spectrum. We
attribute this broadening to Kondo hybridization of the localized f moments
with the conduction electrons. The evolution of the superconducting transition
temperatures in the different members of CeMIn5 can then be understood as a
direct consequence of the strength of this hybridization. Due to the importance
of Kondo spin fluctuations in these materials, we also present calculations
within the non-crossing approximation (NCA) to the Anderson impurity model
including the effect of CEF level splitting for the inelastic neutron
scattering spectra and the magnetic susceptibility.Comment: 30 pages, 6 figures, submitted to Phys. Rev.
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