282,823 research outputs found
Spontaneous and Superfluid Chiral Edge States in Exciton-Polariton Condensates
We present a scheme of interaction-induced topological bandstructures based
on the spin anisotropy of exciton-polaritons in semiconductor microcavities. We
predict theoretically that this scheme allows the engineering of topological
gaps, without requiring a magnetic field or strong spin-orbit interaction
(transverse electric-transverse magnetic splitting). Under non-resonant
pumping, we find that an initially topologically trivial system undergoes a
topological transition upon the spontaneous breaking of phase symmetry
associated with polariton condensation. Under resonant coherent pumping, we
find that it is also possible to engineer a topological dispersion that is
linear in wavevector -- a property associated with polariton superfluidity.Comment: 6 pages, 4 figure
Fluorine Abundances of Galactic Low-Metallicity Giants
With abundances and 2{\sigma} upper limits of fluorine (F) in seven
metal-poor field giants, nucleosynthesis of stellar F at low metallicity is
discussed. The measurements are derived from the HF(1-0) R9 line at 23358{\AA}
using nearinfrared K-band high-resolution spectra obtained with CRIRES at the
Very Large Telescope. The sample reaches lower metallicities than previous
studies on F of field giants, ranging from [Fe/H] = -1.56 down to -2.13.
Effects of three-dimensional model atmospheres on the derived F and O
abundances are quantitatively estimated and shown to be insignificant for the
program stars. The observed F yield in the form of [F/O] is compared with two
sets of Galactic chemical evolution models, which quantitatively demonstrate
the contribution of Type II supernova (SN II) {\nu}-process and asymptotic
giant branch/Wolf-Rayet stars. It is found that at this low-metallicity region,
models cannot well predict the observed distribution of [F/O], while the
observations are better fit by models considering an SN II {\nu}-process with a
neutrino energy of E_{\nu} = 3 x 10^53 erg. Our sample contains HD 110281, a
retrograde orbiting low-{\alpha} halo star, showing a similar F evolution as
globular clusters. This supports the theory that such halo stars are possibly
accreted from dwarf galaxy progenitors of globular clusters in the halo.Comment: 8 pages, 8 figures, 2 tables, published in The Astrophysical Journa
Measurement-induced entanglement of two superconducting qubits
We study the problem of two superconducting quantum qubits coupled via a
resonator. If only one quanta is present in the system and the number of
photons in the resonator is measured with a null result, the qubits end up in
an entangled Bell state. Here we look at one source of errors in this quantum
nondemolition scheme due to the presence of more than one quanta in the
resonator, previous to the measurement. By analyzing the structure of the
conditional Hamiltonian with arbitrary number of quanta, we show that the
scheme is remarkably robust against these type of errors.Comment: 4 pages, 2 figure
Template epitaxial growth of thermoelectric Bi/BiSb superlattice nanowires by charge-controlled pulse electrodeposition
© The Electrochemical Society, Inc. 2009. All rights reserved. Except as provided under U.S. copyright law, this work may not be reproduced, resold, distributed, or modified without the express permission of The Electrochemical Society (ECS). The archival version of this work was published in The Journal of The Electrochemical Society, 156(9), 2009.Bi/BiSb superlattice nanowires (SLNWs) with a controllable and very small bilayer thickness and a sharp segment interface were grown by adopting a charge-controlled pulse electrodeposition. The deposition parameters were optimized to ensure an epitaxial growth of the SLNWs with a preferential orientation. The segment length and bilayer thickness of the SLNWs can be controlled simply by changing the modulating time, and the consistency of the segment length can be well maintained by our approach. The Bravais law in the electrodeposited nanowires is verified by the SLNW structure. The current–voltage measurement shows that the SLNWs have good electrical conductance, particularly those with a smaller bilayer thickness. The Bi/BiSb SLNWs might have excellent thermoelectric performances.National Natural Science Foundation
of China and the National
Major Project of Fundamental Research for Nanomaterials and
Nanostructures
Hot Nuclear Matter Equation of State with a Three-body Force
The finite temperature Brueckner-Hartree-Fock approach is extended by
introducing a microscopic three-body force. In the framework of the extended
model, the equation of state of hot asymmetric nuclear matter and its isospin
dependence have been investigated. The critical temperature of liquid-gas phase
transition for symmetric nuclear matter has been calculated and compared with
other predictions. It turns out that the three-body force gives a repulsive
contribution to the equation of state which is stronger at higher density and
as a consequence reduces the critical temperature of liquid-gas phase
transition. The calculated energy per nucleon of hot asymmetric nuclear matter
is shown to satisfy a simple quadratic dependence on asymmetric parameter
as in the zero-temperature case. The symmetry energy and its density
dependence have been obtained and discussed. Our results show that the
three-body force affects strongly the high-density behavior of the symmetry
energy and makes the symmetry energy more sensitive to the variation of
temperature. The temperature dependence and the isospin dependence of other
physical quantities, such as the proton and neutron single particle potentials
and effective masses are also studied. Due to the additional repulsion produced
by the three-body force contribution, the proton and neutron single particle
potentials are correspondingly enhanced as similar to the zero-temperature
case.Comment: 16 pages, 8 figure
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