Unusual metamagnetism in CeIrIn5_5

We report a high field investigation (up to 45 T) of the metamagnetic transition in CeIrIn$_5$ with resistivity and de-Haas-van-Alphen (dHvA) effect measurements in the temperature range 0.03-1 K. As the magnetic field is increased the resistivity increases, reaches a maximum at the metamagnetic critical field, and falls precipitously for fields just above the transition, while the amplitude of all measurable dHvA frequencies are significantly attenuated near the metamagnetic critical field. However, the dHvA frequencies and cyclotron masses are not substantially altered by the transition. In the low field state, the resistivity is observed to increase toward low temperatures in a singular fashion, a behavior that is rapidly suppressed above the transition. Instead, in the high field state, the resistivity monotonically increases with temperature with a dependence that is more singular than the iconic Fermi-liquid, temperature-squared, behavior. Both the damping of the dHvA amplitudes and the increased resistivity near the metamagnetic critical field indicate an increased scattering rate for charge carriers consistent with critical fluctuation scattering in proximity to a phase transition. The dHvA amplitudes do not uniformly recover above the critical field, with some hole-like orbits being entirely suppressed at high fields. These changes, taken as a whole, suggest that the metamagnetic transition in CeIrIn$_5$ is associated with the polarization and localization of the heaviest of quasiparticles on the hole-like Fermi surface.Comment: 29 pages, 9 figure

Superconductivity and Field-Induced Magnetism in Pr2−x_{2-x}Cex_xCuO4_4 Single Crystals

We report muon-spin rotation/relaxation (muSR) measurements on single crystals of the electron-doped high-T_c superconductor Pr$_{2-x}$Ce$_x$CuO$_4$. In zero external magnetic field, superconductivity is found to coexist with Cu spins that are static on the muSR time scale. In an applied field, we observe a Knight shift that is primarily due to the magnetic moment induced on the Pr ions. Below the superconducting transition temperature T_c, an additional source of static magnetic order appears throughout the sample. This finding is consistent with antiferromagnetic ordering of the Cu spins in the presence of vortices. We also find that the temperature dependence of the in-plane magnetic penetration depth in the vortex state resembles that of the hole-doped cuprates at temperatures above ~ 0.2 T_c.Comment: 4 pages, 5 figure

Heat Capacity in Magnetic and Electric Fields Near the Ferroelectric Transition in Tri-Glycine Sulfate

Specific-heat measurements are reported near the Curie temperature ($T_C$~= 320 K) on tri-glycine sulfate. Measurements were made on crystals whose surfaces were either non-grounded or short-circuited, and were carried out in magnetic fields up to 9 T and electric fields up to 220 V/cm. In non-grounded crystals we find that the shape of the specific-heat anomaly near $T_C$ is thermally broadened. However, the anomaly changes to the characteristic sharp $\lambda$-shape expected for a continuous transition with the application of either a magnetic field or an electric field. In crystals whose surfaces were short-circuited with gold, the characteristic $\lambda$-shape appeared in the absence of an external field. This effect enabled a determination of the critical exponents above and below $T_C$, and may be understood on the basis that the surface charge originating from the pyroelectric coefficient, $dP/dT$, behaves as if shorted by external magnetic or electric fields.Comment: 4 Pages, 4 Figures. To Appear in Applied Physics Letters_ January 200

A New Heavy-Fermion Superconductor CeIrIn5: Relative of the Cuprates?

CeIrIn5 is a member of a new family of heavy-fermion compounds and has a Sommerfeld specific heat coefficient of 720 mJ/mol-K2. It exhibits a bulk, thermodynamic transition to a superconducting state at Tc=0.40 K, below which the specific heat decreases as T2 to a small residual T-linear value. Surprisingly, the electrical resistivity drops below instrumental resolution at a much higher temperature T0=1.2 K. These behaviors are highly reproducible and field-dependent studies indicate that T0 and Tc arise from the same underlying electronic structure. The layered crystal structure of CeIrIn5 suggests a possible analogy to the cuprates in which spin/charge pair correlations develop well above Tc

Rosa hybrid gene GAPC is mutated in the presence of the Rose Rosette Virus

Rose Rosette Disease (RRD) harms the global rose supply by modification of the growth and development in rose cultivar. RRD spreads via a negative-sense RNA plant virus transmitted by eriophyid mites. Importantly, there is no pre-existing knowledge about the biochemistry by which this virus debilitates roses. Here we implicate glyceraldehyde-3-phosphate dehydrogenase (GAPDH), one of the major metabolic enzymes in plants, as a possible target of the virus. Genomic DNA of the cytosolic form of the protein encoded by GAPC was extracted from both virally-infected and non-infected samples of the Rosa hybrid cultivar Rosa Tropicana. The sequence results provided several distinct differences in the GAPC gene of the non-infected rose compared to the virally-infected rose. Importantly, these modified nucleotide bases resulted in a putative protein sequence containing four unique non-conserved amino acid substitutions in the GAPDH enzyme. This study provides the first evidence of a gene impacted in virally-infected rose plants

Depleted Kondo Lattices

We consider a two dimensional Kondo lattice model with exchange J and hopping t in which three out of four impurity spins are removed in a regular way. At the particle-hole symmetric point the model may be studied with auxiliary field quantum Monte Carlo methods without sign problems. To achieve the relevant energy scales on finite clusters, we introduce a simple method to reduce size effects by up to an order of magnitude in temperature. In this model, a metallic phase survives up to arbitrarily low temperatures before being disrupted by magnetic fluctuations which open a gap in the charge sector. We study the formation of the heavy-electron state with emphasis on a crossover scale T* defined by the maximum in the resistivity versus temperature curve. The behavior of thermodynamic properties such as specific heat as well as spin and charge uniform susceptibilities are studied as the temperature varies in a wide range across T*. Within our accuracy T* compares well to the Kondo scale of the related single impurity problem. Finally our QMC resuls are compared with mean-field approximations.Comment: 12 pages, 13 figures. Submitted to Phys. Rev.

Multiple aneurysms in childhood

AbstractArterial aneurysms in children are rare. When present, they are often associated with connective tissue disorders or arteritidies. Idiopathic aneurysms occurring at multiple sites throughout the arterial tree are rare, with only ten cases reported. This report describes a case of multiple arterial aneurysms of uncertain origin involving upper-extremity, extracranial cerebrovascular, aortoiliac, and renal arteries in a 14-year-old boy. The clinical presentation, vascular reconstruction, pathologic findings, and a brief review of the literature are described

Coexistence of magnetism and superconductivity in CeRh1-xIrxIn5

We report a thermodynamic and transport study of the phase diagram of CeRh1-xIrxIn5. Superconductivity is observed over a broad range of doping, 0.3 < x < 1, including a substantial range of concentration (0.3 < x <0.6) over which it coexists with magnetic order (which is observed for 0 < x < 0.6). The anomalous transition to zero resistance that is observed in CeIrIn5 is robust against Rh substitution. In fact, the observed bulk Tc in CeRh0.5Ir0.5In5 is more than double that of CeIrIn5, whereas the zero-resistance transition temperature is relatively unchanged for 0.5 < x < 1

Anomalous f-electron Hall Effect in the Heavy-Fermion System CeTIn5_{5} (T = Co, Ir, or Rh)

The in-plane Hall coefficient $R_{H}(T)$ of CeRhIn$_{5}$, CeIrIn$_{5}$, and CeCoIn$_{5}$ and their respective non-magnetic lanthanum analogs are reported in fields to 90 kOe and at temperatures from 2 K to 325 K. $R_{H}(T)$ is negative, field-independent, and dominated by skew-scattering above $\sim$ 50 K in the Ce compounds. $R_{H}(H \to 0)$ becomes increasingly negative below 50 K and varies with temperature in a manner that is inconsistent with skew scattering. Field-dependent measurements show that the low-T anomaly is strongly suppressed when the applied field is increased to 90 kOe. Measurements on LaRhIn$_{5}$, LaIrIn$_{5}$, and LaCoIn$_{5}$ indicate that the same anomalous temperature dependence is present in the Hall coefficient of these non-magnetic analogs, albeit with a reduced amplitude and no field dependence. Hall angle ($\theta_{H}$) measurements find that the ratio $\rho_{xx}/\rho_{xy}=\cot(\theta_{H})$ varies as $T^{2}$ below 20 K for all three Ce-115 compounds. The Hall angle of the La-115 compounds follow this T-dependence as well. These data suggest that the electronic-structure contribution dominates the Hall effect in the 115 compounds, with $f$-electron and Kondo interactions acting to magnify the influence of the underlying complex band structure. This is in stark contrast to the situation in most $4f$ and $5f$ heavy-fermion compounds where the normal carrier contribution to the Hall effect provides only a small, T-independent background to $R_{H}.$Comment: 23 pages and 8 figure