265 research outputs found
Charge-Doping driven Evolution of Magnetism and non-Fermi-Liquid Behavior in the Filled Skutterudite CePt4Ge12-xSbx
The filled-skutterudite compound CePt4Ge12 is situated close to the border
between intermediate-valence of Ce and heavy-fermion behavior. Substitution of
Ge by Sb drives the system into a strongly correlated and ultimately upon
further increasing the Sb concentration into an antiferromagnetically ordered
state. Our experiments evidence a delicate interplay of emerging Kondo physics
and the formation of a local 4f moment. An extended non-Fermi-liquid region,
which can be understood in the framework of a Kondo-disorder model, is
observed. Band-structure calculations support the conclusion that the physical
properties are governed by the interplay of electron supply via Sb substitution
and the concomitant volume effects.Comment: 5 pages, 3 Figur
Heat-capacity measurements under uniaxial pressure using a piezo-driven device
Y.S.L. acknowledges the support of a St Leonards scholarship from the University of St Andrews, the Engineering and Physical Sciences Research Council via the Scottish Condensed Matter Centre for Doctoral Training under Grant No. EP/G03673X/1, and the Max Planck Society.We report the development of a technique to measure heat capacity at large uniaxial pressure using a piezoelectric-driven device generating compressive and tensile strain in the sample. Our setup is optimized for temperatures ranging from 8 K down to millikelvin. Using an AC heat-capacity technique, we are able to achieve an extremely high resolution and to probe a homogeneously strained part of the sample. We demonstrate the capabilities of our setup on the unconventional superconductor Sr2RuO4. By replacing thermometer and adjusting the remaining setup accordingly, the temperature regime of the experiment can be adapted to other temperature ranges of interest.Publisher PDFPeer reviewe
Superconducting pairing symmetry in MoTe
Topological superconductors have long been sought for their potential use in
quantum computing. The type-II Weyl semimetal MoTe is an obvious
candidate, exhibiting a superconducting state below 500 mK at ambient pressure,
but the question remains whether the pairing is conventional or
topological . The application of external pressure favors the
superconducting state in MoTe and suppresses the structural transition
from to . The competition between the two structures leads to a
mixed phase that strongly enhances the disorder present in the system,
remarkably without affecting the superconducting transition temperature, in
contrast to the expectation of pairing superconductivity. Our thorough
analysis of the electrical and Hall resistivities as a function of pressure
yields the most accurate temperature-pressure phase diagram available to date
for MoTe and a detailed view of the relationship between disorder and
superconductivity, supporting a conventional pairing symmetry
Magnetism and unconventional superconductivity in CeMIn heavy-fermion crystals
We review magnetic, superconducting and non-Fermi-liquid properties of the
structurally layered heavy-fermion compounds CeMIn (M=Co, Rh,
Ir). These properties suggest d-wave superconductivity and proximity to an
antiferromagetic quantum-critical point.Comment: submitted 23rd International Conference on Low Temperature Physics
(LT-23), Aug. 200
The Bivariate Normal Copula
We collect well known and less known facts about the bivariate normal
distribution and translate them into copula language. In addition, we prove a
very general formula for the bivariate normal copula, we compute Gini's gamma,
and we provide improved bounds and approximations on the diagonal.Comment: 24 page
Response of the Heavy-Fermion Superconductor CeCoIn to Pressure: Roles of Dimensionality and Proximity to a Quantum-Critical Point
We report measurements of the pressure-dependent superconducting transition
temperature and electrical resistivity of the heavy-fermion compound
CeCoIn. Pressure moves CeCoIn away from its proximity to a
quantum-critical point at atmospheric pressure. Experimental results are
qualitatively consistent with theoretical predictions for strong-coupled,
d-wave superconductivity in an anisotropic 3D superconductor.Comment: 9 pages, 5 figure
Ambient-pressure bulk superconductivity deep in the magnetic state of CeRhIn5
Specific heat, magnetic susceptibility and electrical transport measurements
were performed at ambient pressure on high-quality single crystal specimens of
CeRhIn5 down to ultra-low temperatures. We report signatures of an anomaly
observed in all measured quantities consistent with a bulk phase transition to
a superconducting state at T_c=110 mK. Occurring far below the onset of
antiferromagnetism at T_N=3.8 K, this transition appears to involve a
significant portion of the available low-temperature density of electronic
states, exhibiting an entropy change in line with that found in other members
of the 115 family of superconductors tuned away from quantum criticality.Comment: 4 pages, 4 figure
Optimal treatment allocations in space and time for on-line control of an emerging infectious disease
A key component in controlling the spread of an epidemic is deciding where, whenand to whom to apply an intervention.We develop a framework for using data to informthese decisionsin realtime.We formalize a treatment allocation strategy as a sequence of functions, oneper treatment period, that map up-to-date information on the spread of an infectious diseaseto a subset of locations where treatment should be allocated. An optimal allocation strategyoptimizes some cumulative outcome, e.g. the number of uninfected locations, the geographicfootprint of the disease or the cost of the epidemic. Estimation of an optimal allocation strategyfor an emerging infectious disease is challenging because spatial proximity induces interferencebetween locations, the number of possible allocations is exponential in the number oflocations, and because disease dynamics and intervention effectiveness are unknown at outbreak.We derive a Bayesian on-line estimator of the optimal allocation strategy that combinessimulation–optimization with Thompson sampling.The estimator proposed performs favourablyin simulation experiments. This work is motivated by and illustrated using data on the spread ofwhite nose syndrome, which is a highly fatal infectious disease devastating bat populations inNorth America
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