Effect of annealing on glassy dynamics and non-Fermi liquid behavior in UCu_4Pd

Longitudinal-field muon spin relaxation (LF-muSR) experiments have been performed in unannealed and annealed samples of the heavy-fermion compound UCu_4Pd to study the effect of disorder on non-Fermi liquid behavior in this material. The muon spin relaxation functions G(t,H) obey the time-field scaling relation G(t,H) = G(t/H^gamma) previously observed in this compound. The observed scaling exponent gamma = 0.3 pm 0.1, independent of annealing. Fits of the stretched-exponential relaxation function G(t) = exp[-(Lambda t)^K] to the data yielded stretching exponentials K < 1 for all samples. Annealed samples exhibited a reduction of the relaxation rate at low temperatures, indicating that annealing shifts fluctuation noise power to higher frequencies. There was no tendency of the inhomogeneous spread in rates to decrease with annealing, which modifies but does not eliminate the glassy spin dynamics reported previously in this compound. The correlation with residual resistivity previously observed for a number of NFL heavy-electron materials is also found in the present work.Comment: 4 pages, 3 figures, submitted to 10th International Conference on Muon Spin Rotation, Relaxation, and Resonance, Oxford, UK, August 200

Quasi particle interference of heavy fermions in resonant x ray scattering

Resonant x ray scattering RXS has recently become an increasingly important tool for the study of ordering phenomena in correlated electron systems. Yet, the interpretation of RXS experiments remains theoretically challenging because of the complexity of the RXS cross section. Central to this debate is the recent proposal that impurity induced Friedel oscillations, akin to quasi particle interference signals observed with a scanning tunneling microscope STM , can lead to scattering peaks in RXS experiments. The possibility that quasi particle properties can be probed in RXSmeasurements opens up a new avenue to study the bulk band structure ofmaterials with the orbital and element selectivity provided by RXS. We test these ideas by combining RXS and STM measurements of the heavy fermion compound CeMIn5 M Co, Rh . Temperature and doping dependent RXSmeasurements at the Ce M4 edge show abroad scattering enhancement that correlateswith the appearance of heavy f electron bands in these compounds. The scattering enhancement is consistentwith themeasured quasi particle interference signal in the STMmeasurements, indicating that the quasi particle interference can be probed through the momentum distribution of RXS signals. Overall, our experiments demonstrate new opportunities for studies of correlated electronic systems using the RXS techniqu

Associations of autozygosity with a broad range of human phenotypes

In many species, the offspring of related parents suffer reduced reproductive success, a phenomenon known as inbreeding depression. In humans, the importance of this effect has remained unclear, partly because reproduction between close relatives is both rare and frequently associated with confounding social factors. Here, using genomic inbreeding coefficients (F-ROH) for >1.4 million individuals, we show that F-ROH is significantly associated (p <0.0005) with apparently deleterious changes in 32 out of 100 traits analysed. These changes are associated with runs of homozygosity (ROH), but not with common variant homozygosity, suggesting that genetic variants associated with inbreeding depression are predominantly rare. The effect on fertility is striking: F-ROH equivalent to the offspring of first cousins is associated with a 55% decrease [95% CI 44-66%] in the odds of having children. Finally, the effects of F-ROH are confirmed within full-sibling pairs, where the variation in F-ROH is independent of all environmental confounding.Peer reviewe

Electronic structure and magnetism in the layered triangular lattice compound CeAuAl4Ge2

Results are reported for the f-electron intermetallic CeAuAl4Ge2, where the atomic arrangement of the cerium ions creates the conditions for possible geometric frustration. The magnetic susceptibility follows a Curie-Weiss temperature dependence at elevated temperatures, revealing that the cerium ions are trivalent. At lower temperatures the crystal electric field splits the Hund&apos;s rule multiplet, resulting in a weak low-temperature magnetic exchange interaction and ordering near TM≈1.4K. This occurs within a metallic Kondo lattice, where electrical resistivity and heat capacity measurements show that the Kondo-driven electronic correlations are negligible. Quantum oscillations are detected in ac-magnetic susceptibility measurements and uncover small charge carrier effective masses. Electronic structure calculations reveal that inclusion of an on-f-site Coulomb repulsion (Hubbard) U results in antiferromagnetic order and causes the f-electron bands to move away from the Fermi level, resulting in electronic behavior that is dominated by the s,p, and d bands, which are all characterized by light electron masses. Thus, CeAuAl4Ge2 may provide a starting point for investigating geometric magnetic frustration in a cerium lattice without strong Kondo hybridization, where calculations provide useful guidance. © 2017 American Physical Society

Converting topological insulators into topological metals within the tetradymite family

International audienceWe report the electronic band structures and concomitant Fermi surfaces for a family of exfoliable tetradymite compounds with the formula T 2 C h 2 P n , obtained as a modification to the well-known topological insulator binaries Bi 2 ( Se , Te ) 3 by replacing one chalcogen ( C h ) with a pnictogen ( P n ) and Bi with the tetravalent transition metals T = Ti, Zr, or Hf. This imbalances the electron count and results in layered metals characterized by relatively high carrier mobilities and bulk two-dimensional Fermi surfaces whose topography is well-described by first-principles calculations. Intriguingly, slab electronic structure calculations predict Dirac-like surface states. In contrast to Bi 2 Se 3 , where the surface Dirac bands are at the Γ point, for ( Zr , Hf ) 2 Te 2 (P,As) there are Dirac cones of strong topological character around both the ¯¯¯ Γ and ¯¯¯¯ M points, which are above and below the Fermi energy, respectively. For Ti 2 Te 2 P , the surface state is predicted to exist only around the ¯¯¯¯ M point. In agreement with these predictions, the surface states that are located below the Fermi energy are observed by angle-resolved photoemission spectroscopy measurements, revealing that they coexist with the bulk metallic state. Thus this family of materials provides a foundation upon which to develop novel phenomena that exploit both the bulk and surface states (e.g., topological superconductivity)

Relationship between granulocyte macrophage-colony stimulating factor, tumour necrosis factor-α and Trypanosoma cruzi infection of murine macrophages

Gamma interferon (IFN-γ)-activated macrophages control Trypanosoma cruzi infection via nitric oxide (NO), recently recognized as a major effector molecule. Granulocyte macrophage-colony stimulating factor (GM-CSF) is a multipotent cytokine secreted by macrophages and many other cells. It induces the production of tumour necrosis factor alpha (TNF-α), another cytokine also secreted by macrophages and involved in the control of T. cruzi infection. However, no data are available on the relationship between GM-CSF, TNF-α and NO produced by macrophages activated by IFN-γ and infected with T. cruzi. To highlight this relationship, mouse peritoneal macrophages (MPM) and two c-myc retrovirus-induced macrophage cell lines (9.1.1 and BMM8), respectively characterized by a constitutive and an inducible production of GM-CSF, were activated with IFN-γ and/or GM-CSF and infected with T, cruzi. Our results indicate that T. cruzi upregulates GM-CSF release from MPM and from the two macrophage cell lines, activated (or not) by IFN-γ. A high autocrine production of GM-CSF or an exogenous supply of GM-CSF is correlated with an enhanced release of TNF-α and NO, inducing an improved control of T. cruzi infection by IFN-γ-activated MPM.SCOPUS: ar.jFLWNAinfo:eu-repo/semantics/publishe