Renormalized parameters and perturbation theory for an n-channel Anderson model with Hund's rule coupling: Asymmetric case

We explore the predictions of the renormalized perturbation theory for an n-channel Anderson model, both with and without Hund's rule coupling, in the regime away from particle-hole symmetry. For the model with n=2 we deduce the renormalized parameters from numerical renormalization group calculations, and plot them as a function of the occupation at the impurity site, nd. From these we deduce the spin, orbital and charge susceptibilities, Wilson ratios and quasiparticle density of states at T=0, in the different parameter regimes, which gives a comprehensive overview of the low energy behavior of the model. We compare the difference in Kondo behaviors at the points where nd=1 and nd=2. One unexpected feature of the results is the suppression of the charge susceptibility in the strong correlation regime over the occupation number range 1 <nd <3.Comment: 9 pages, 17 figure

Fermi Liquids and the Luttinger Integral

The Luttinger Theorem, which relates the electron density to the volume of the Fermi surface in an itinerant electron system, is taken to be one of the essential features of a Fermi liquid. The microscopic derivation of this result depends on the vanishing of a certain integral, the Luttinger integral $I_{\rm L}$, which is also the basis of the Friedel sum rule for impurity models, relating the impurity occupation number to the scattering phase shift of the conduction electrons. It is known that non-zero values of $I_{\rm L}$ with $I_{\rm L}=\pm\pi/2$, occur in impurity models in phases with non-analytic low energy scattering, classified as singular Fermi liquids. Here we show the same values, $I_{\rm L}=\pm\pi/2$, occur in an impurity model in phases with regular low energy Fermi liquid behavior. Consequently the Luttinger integral can be taken to characterize these phases, and the quantum critical points separating them interpreted as topological.Comment: 5 pages 7 figure

Orbitally-driven Behavior: Mott Transition, Quantum Oscillations and Colossal Magnetoresistance in Bilayered Ca3Ru2O7

We report recent transport and thermodynamic experiments over a wide range of temperatures for the Mott-like system Ca3Ru2O7 at high magnetic fields, B, up to 30 T. This work reveals a rich and highly anisotropic phase diagram, where applying B along the a-, b-, and c-axis leads to vastly different behavior. A fully spin-polarized state via a first order metamagnetic transition is obtained for B||a, and colossal magnetoresistance is seen for B||b, and quantum oscillations in the resistivity are observed for B||c, respectively. The interplay of the lattice, orbital and spin degrees of freedom are believed to give rise to this strongly anisotropic behavior.Comment: 26 pages and 8 figure

Kufor-Rakeb syndrome, pallido-pyramidal degeneration with supranuclear upgaze paresis and dementia, maps to 1p36

Kufor-Rakeb syndrome is an autosomal recessive nigro-striatal-pallidal-pyramidal neurodegeneration. The onset is in the teenage years with clinical features of Parkinson’s disease plus spasticity, supranuclear upgaze paresis, and dementia. Brain scans show atrophy of the globus pallidus and pyramids and, later, widespread cerebral atrophy. We report linkage in Kufor- Rakeb syndrome to a 9 cM region of chromosome 1p36 delineated by the markers D1S436 and D1S2843, with a maximum multipoint lod score of 3.6. (J Med Genet 2001;38:680–682

Autosomal recessive primary microcephaly: an analysis of locus heterogeneity and phenotypic variation

BACKGROUND AND OBJECTIVES: Locus heterogeneity is well established in autosomal recessive primary microcephaly (MCPH) and to date five loci have been mapped. However, the relative contributions of these loci have not been assessed and genotype-phenotype correlations have not been investigated. DESIGN: A study population of 56 consanguineous families resident in or originating from northern Pakistan was ascertained and assessed by the authors. A panel of microsatellite markers spanning each of the MCPH loci was designed, against which the families were genotyped. RESULTS: The head circumference of the 131 affected subjects ranged from 4 to 14 SD below the mean, but there was little intrafamilial variation among affecteds (± 1 SD). MCPH5 was the most prevalent, with 24/56 families consistent with linkage; 2/56 families were compatible with linkage to MCPH1, 10/56 to MCPH2, 2/56 to MCPH3, none to MCPH4, and 18/56 did not segregate with any of the loci. CONCLUSIONS: MCPH5 is the most common locus in this population. On clinical grounds alone, the phenotype of families linked to each MCPH locus could not be distinguished. We have also shown that further MCPH loci await discovery with a number of families as yet unlinked

Fermi liquids and the Luttinger integral

The Luttinger Theorem, which relates the electron density to the volume of the Fermi surface in an itinerant electron system, is taken to be one of the essential features of a Fermi liquid. The microscopic derivation of this result depends on the vanishing of a certain integral, the Luttinger integral I L, which is also the basis of the Friedel sum rule for impurity models, relating the impurity occupation number to the scattering phase shift of the conduction electrons. It is known that non-zero values of I L with I L = ±π/2, occur in impurity models classified as singular Fermi liquids. Here we show the same values, I L = ±π/2, occur in an impurity model in phases with regular low energy Fermi liquid behavior. Consequently the Luttinger integral can be taken to characterize these phases, and the quantum critical points separating them interpreted as topological

Progress in High Resolution Scanning Ion Microscopy and Secondary Ion Mass Spectrometry Imaging Microanalysis

The performance of a new high resolution scanning ion microprobe (SIM) is elucidated with regard to imaging capabilities using the ion-induced secondary electron (ISE) or secondary ion (ISI) signals, and the mass-resolved signal from a secondary ion mass spectrometry (SIMS) system. The new instrument focuses a beam extracted from a liquid metal ion source (LMIS) to a range of spot sizes reaching the 20 nm level. The probe current (1.6 pA) available at this level of lateral resolution, which approaches the theoretical resolution limits of the SIMS method, is still adequate to obtain detailed isotopic maps for surfaces rich in the elements of low ionization potential (positive ISI), or high electron affinity (negative ISI). In addition to examples of high resolution ISE and ISI images of objects displaying sufficiently small topographic detail, mass spectra and isotopic maps are shown, testing both the lateral and depth resolution attained. The latter results belong with a program of interdisciplinary research applications of the new microprobe, which include studies of e.g., the monolayer lateral distribution of intercalant in SbCl5 intercalated graphite and of silicate minerals and iron distribution in sections of chondrules and their rims (components of chondrites, a class of stoney meteorites). In the biomedical field, the new microprobe finds application in e.g., the study of human renal calculi and bone. Most promising is the use of stable isotope tracers (e.g., Ca44) to unravel the dynamics of bone mineralization, as thus far shown with the in-vitro culture of the skull bone of neonatal mice