6,096 research outputs found
LDA+DMFT Approach to Magnetocrystalline Anisotropy of Strong Magnets
The new challenges posed by the need of finding strong rare-earth free
magnets demand methods that can predict magnetization and magnetocrystalline
anisotropy energy (MAE). We argue that correlated electron effects, which are
normally underestimated in band structure calculations, play a crucial role in
the development of the orbital component of the magnetic moments. Because
magnetic anisotropy arises from this orbital component, the ability to include
correlation effects has profound consequences on our predictive power of the
MAE of strong magnets. Here we show that incorporating the local effects of
electronic correlations with dynamical mean-field theory provides reliable
estimates of the orbital moment, the mass enhancement and the MAE of YCo5.Comment: 7 pages, 4 figures, published versio
Improving teleportation of continuous variables by local operations
We study a continuous-variable (CV) teleportation protocol based on a shared
entangled state produced by the quantum-nondemolition (QND) interaction of two
vacuum states. The scheme utilizes the QND interaction or an unbalanced beam
splitter in the Bell measurement. It is shown that in the non-unity gain regime
the signal transfer coefficient can be enhanced while the conditional variance
product remains preserved by applying appropriate local squeezing operation on
sender's part of the shared entangled state. In the unity gain regime it is
demonstrated that the fidelity of teleportation can be increased with the help
of the local squeezing operations on parts of the shared entangled state that
convert effectively our scheme to the standard CV teleportation scheme.
Further, it is proved analytically that such a choice of the local symplectic
operations minimizes the noise by which the mean number of photons in the input
state is increased during the teleportation. Finally, our analysis reveals that
the local symplectic operation on sender's side can be integrated into the Bell
measurement if the interaction constant of the interaction in the Bell
measurement can be adjusted properly.Comment: 10 pages, 1 figure, discussion of the non-unity gain teleportation is
adde
Intertwined Orders in Heavy-Fermion Superconductor CeCoIn
The appearance of spin-density-wave (SDW) magnetic order in the
low-temperature and high-field corner of the superconducting phase diagram of
CeCoIn is unique among unconventional superconductors. The nature of this
magnetic phase is a matter of current debate. Here, we present the thermal
conductivity of CeCoIn in a rotating magnetic field, which reveals the
presence of an additional order inside the phase that is intimately
intertwined with the superconducting -wave and SDW orders. A discontinuous
change of the thermal conductivity within the phase, when the magnetic
field is rotated about antinodes of the superconducting -wave order
parameter, demands that the additional order must change abruptly together with
the recently observed switching of the SDW. A combination of interactions,
where spin-orbit coupling orients the SDW, which then selects the secondary
-wave pair-density-wave component (with an average amplitude of 20\% of the
primary -wave order parameter), accounts for the observed behavior
Field induced density wave in the heavy fermion compound CeRhIn5
Metals containing Ce often show strong electron correlations due to the
proximity of the 4f state to the Fermi energy, leading to strong coupling with
the conduction electrons. This coupling typically induces a variety of
competing ground states, including heavy-fermion metals, magnetism and
unconventional superconductivity. The d-wave superconductivity in CeTMIn5
(TM=Co, Rh, Ir) has attracted significant interest due to its qualitative
similarity to the cuprate high-Tc superconductors. Here, we show evidence for a
field induced phase-transition to a state akin to a density-wave (DW) in the
heavy fermion CeRhIn5, existing in proximity to its unconventional
superconductivity. The DW state is signaled by a hysteretic anomaly in the
in-plane resistivity accompanied by the appearance of non-linear electrical
transport at high magnetic fields (>27T), which are the distinctive
characteristics of density-wave states. The unusually large hysteresis enables
us to directly investigate the Fermi surface of a supercooled electronic system
and to clearly associate a Fermi surface reconstruction with the transition.
Key to our observation is the fabrication of single crystal microstructures,
which are found to be highly sensitive to "subtle" phase transitions involving
only small portions of the Fermi surface. Such subtle order might be a common
feature among correlated electron systems, and its clear observation adds a new
perspective on the similarly subtle CDW state in the cuprates.Comment: Accepted in Nature Communication
Purification and detection of entangled coherent states
In [J. C. Howell and J. A. Yeazell, Phys. Rev. A 62, 012102 (2000)], a
proposal is made to generate entangled macroscopically distinguishable states
of two spatially separated traveling optical modes. We model the decoherence
due to light scattering during the propagation along an optical transmission
line and propose a setup allowing an entanglement purification from a number of
preparations which are partially decohered due to transmission. A purification
is achieved even without any manual intervention. We consider a nondemolition
configuration to measure the purity of the state as contrast of interference
fringes in a double-slit setup. Regarding the entangled coherent states as a
state of a bipartite quantum system, a close relationship between purity and
entanglement of formation can be obtained. In this way, the contrast of
interference fringes provides a direct means to measure entanglement.Comment: 9 pages, 6 figures, using Revtex
Methodology of the biological risk classification of animal pathogens in Belgium
The biological hazards posed by micro-organisms have lead to their categorisation into risk groups and the elaboration of classification lists. Current classification systems rely on criteria defined by the World Health Organization, which cover the severity of the disease the micro-organism might cause, its ability to spread and the availability of prophylaxis or efficient treatment. Animal pathogens are classified according to the definitions of the World Organization of Animal Health, which also consider economic aspects of disease. In Europe, classification is often directly linked to containment measures. The Belgian classification system however, only considers the inherent characteristics of the micro-organism, not its use, making the risk classification independent of containment measures. A common classification list for human and animal pathogens has been developed in Belgium using as comprehensive an approach as possible. Evolution of scientific knowledge will demand regular updating of classification lists. This paper describes the Belgian risk classification system and the methodology that was used for its peer-reviewed revision (with a focus on animal pathogens)
Large magnetic penetration depth and thermal fluctuations in a Ca(PtAs)[(FePt)As] (x=0.097) single crystal
We have measured the temperature dependence of the absolute value of the
magnetic penetration depth in a
Ca(PtAs)[(FePt)As] (x=0.097)
single crystal using a low-temperature magnetic force microscope (MFM). We
obtain (0)1000 nm via extrapolating the data to .
This large and pronounced anisotropy in this system are responsible
for large thermal fluctuations and the presence of a liquid vortex phase in
this low-temperature superconductor with critical temperature of 11 K,
consistent with the interpretation of the electrical transport data. The
superconducting parameters obtained from and coherence length
place this compound in the extreme type \MakeUppercase{\romannumeral 2} regime.
Meissner responses (via MFM) at different locations across the sample are
similar to each other, indicating good homogeneity of the superconducting state
on a sub-micron scale
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