1,961 research outputs found
Thermodynamic evidence for valley-dependent density of states in bulk bismuth
Electron-like carriers in bismuth are described by the Dirac Hamiltonian,
with a band mass becoming a thousandth of the bare electron mass along one
crystalline axis. The existence of three anisotropic valleys offers electrons
an additional degree of freedom, a subject of recent attention. Here, we map
the Landau spectrum by angle-resolved magnetostriction, and quantify the
carrier number in each valley: while the electron valleys keep identical
spectra, they substantially differ in their density of states at the Fermi
level. Thus, the electron fluid does not keep the rotational symmetry of the
lattice at low temperature and high magnetic field, even in the absence of
internal strain. This effect, reminiscent of the Coulomb pseudo-gap in
localized electronic states, affects only electrons in the immediate vicinity
of the Fermi level. It presents the most striking departure from the
non-interacting picture of electrons in bulk bismuth.Comment: 6 pages, 3 Figure
Uniaxial stress tuning of geometrical frustration in a Kondo lattice
Hexagonal CeRhSn with paramagnetic moments on a distorted Kagome lattice
displays zero-field quantum critical behavior related to geometrical
frustration. We report high-resolution thermal expansion and magnetostriction
measurements under multiextreme conditions such as uniaxial stress up to 200
MPa, temperatures down to 0.1 K and magnetic fields up to 10 T. Under uniaxial
stress along the -direction, quantum criticality disappears and a complex
magnetic phase diagram arises with a sequence of phases below 1.2 K and fields
between 0 and 3 T (). Since the Kondo coupling increases with
stress, which alone would stabilize paramagnetic behavior in CeRhSn, the
observed order arises from the release of geometrical frustration by in-plane
stress.Comment: Accepted in PRB Rapid Com
Phase Rotation, Cooling And Acceleration Of Muon Beams: A Comparison Of Different Approaches
Experimental and theoretical activities are underway at CERN with the aim of
examining the feasibility of a very-high-flux neutrino source. In the present
scheme, a high-power proton beam (some 4 MW) bombards a target where pions are
produced. The pions are collected and decay to muons under controlled optical
condition. The muons are cooled and accelerated to a final energy of 50 GeV
before being injected into a decay ring where they decay under well-defined
conditions of energy and emittance.
We present the most challenging parts of the whole scenario, the muon
capture, the ionisation-cooling and the first stage of the muon acceleration.
Different schemes, their performance and the technical challenges are compared.Comment: LINAC 2000 CONFERENCE, paper ID No. THC1
Cascade of magnetic field induced Lifshitz transitions in the ferromagnetic Kondo lattice material YbNi4P2
A ferromagnetic quantum critical point is thought not to exist in two and
three-dimensional metallic systems yet is realized in the Kondo lattice
compound YbNi4(P,As)2, possibly due to its one-dimensionality. It is crucial to
investigate the dimensionality of the Fermi surface of YbNi4P2 experimentally
but common probes such as ARPES and quantum oscillation measurements are
lacking. Here, we studied the magnetic field dependence of transport and
thermodynamic properties of YbNi4P2. The Kondo effect is continuously
suppressed and additionally we identify nine Lifshitz transitions between 0.4
and 18 T. We analyze the transport coefficients in detail and identify the type
of Lifshitz transitions as neck or void type to gain information on the Fermi
surface of YbNi4P2. The large number of Lifshitz transitions observed within
this small energy window is unprecedented and results from the particular flat
renormalized band structure with strong 4f-electron character shaped by the
Kondo lattice effect.Comment: 6 pages, 4 figure
Influenza A virus OP7 defective interfering particles: Cell culture-based production and antiviral efficacy in vivo
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Emission properties of YAG: Ce ceramics with barium fluoride flux
In this work, we investigated the luminescent properties of YAG, Ce ceramics with an addition of barium fluoride flux. The ceramic samples were sintered from obtained YAG: Ce, BaF2 phosphor powder. Morphological, luminescent and decay time characteristics of YAG: Ce ceramics were investigated. The luminescence decay kinetics analysis of the ceramics showed that the decay time in phosphors and ceramics is different in the visual spectral range
ITSM ProcessGuide – A Process Guidance System for IT Service Management
Process Guidance aims at increasing the process model understanding and effective and efficient process execution. In this paper we present the context, design, implementation, and ongoing evaluation of a Process Guidance System instantiation in an organizational setting. The system is used to support the IT Service Management processes within the case company. It is used productively in the case company of this research and this article describes how the system’s features are designed for the evaluation
Intelligent diagnostic feedback for online multiple-choice questions
When students attempt multiple-choice questions (MCQs) they generate invaluable information which can form the basis for understanding their learning behaviours. In this research, the information is collected and automatically analysed to provide customized, diagnostic feedback to support students’ learning. This is achieved within a web-based system, incorporating the snap-drift neural network based analysis of students’ responses to MCQs. This paper presents the results of a large trial of the method and the system which demonstrates the effectiveness of the feedback in guiding students towards a better understanding of particular concepts
Measurement of the cross-section and charge asymmetry of bosons produced in proton-proton collisions at TeV with the ATLAS detector
This paper presents measurements of the and cross-sections and the associated charge asymmetry as a
function of the absolute pseudorapidity of the decay muon. The data were
collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with
the ATLAS experiment at the LHC and correspond to a total integrated luminosity
of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements
varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the
1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured
with an uncertainty between 0.002 and 0.003. The results are compared with
predictions based on next-to-next-to-leading-order calculations with various
parton distribution functions and have the sensitivity to discriminate between
them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables,
submitted to EPJC. All figures including auxiliary figures are available at
https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13
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