50,641 research outputs found
Medium polarization in asymmetric nuclear matter
The influence of the core polarization on the effective nuclear interaction
of asymmetric nuclear matter is calculated in the framework of the induced
interaction theory. The strong isospin dependence of the density and spin
density fluctuations is studied along with the interplay between the neutron
and proton core polarizations. Moving from symmetric nuclear matter to pure
neutron matter the crossover of the induced interaction from attractive to
repulsive in the spin singlet state is determined as a function of the isospin
imbalance.The density range in which it occurs is also determined. For the spin
triplet state the induced interaction turns out to be always repulsive. The
implications of the results for the neutron star superfluid phases are shortly
discussed.Comment: 6 pages, 4 figure
A hybrid stochastic hierarchy equations of motion approach to treat the low temperature dynamics of non-Markovian open quantum systems
The hierarchical equations of motion technique has found widespread success
as a tool to generate the numerically exact dynamics of non-Markovian open
quantum systems. However, its application to low temperature environments
remains a serious challenge due to the need for a deep hierarchy that arises
from the Matsubara expansion of the bath correlation function. Here we present
a hybrid stochastic hierarchical equation of motion (sHEOM) approach that
alleviates this bottleneck and leads to a numerical cost that is nearly
independent of temperature. Additionally, the sHEOM method generally converges
with fewer hierarchy tiers allowing for the treatment of larger systems.
Benchmark calculations are presented on the dynamics of two level systems at
both high and low temperatures to demonstrate the efficacy of the approach.
Then the hybrid method is used to generate the exact dynamics of systems that
are nearly impossible to treat by the standard hierarchy. First, exact energy
transfer rates are calculated across a broad range of temperatures revealing
the deviations from the Forster rates. This is followed by computations of the
entanglement dynamics in a system of two qubits at low temperature spanning the
weak to strong system-bath coupling regimes.Comment: 20 pages, 6 figure
Optical control of the spin state of two Mn atoms in a quantum dot
We report on the optical spectroscopy of the spin of two magnetic atoms (Mn)
embedded in an individual quantum dot interacting with either a single
electron, a single exciton and single trion. As a result of their interaction
to a common entity, the Mn spins become correlated. The dynamics of this
process is probed by time resolved spectroscopy, that permits to determine the
optical orientation time in the range of a few tens of . In addition, we
show that the energy of the collective spin states of the two Mn atoms can be
tuned through the optical Stark effect induced by a resonant laser field
Pinned Low Energy Electronic Excitation in Metal Exchanged Vanadium Oxide Nanoscrolls
We measured the optical properties of mixed valent vanadium oxide nanoscrolls
and their metal exchanged derivatives in order to investigate the charge
dynamics in these compounds. In contrast to the prediction of a metallic state
for the metal exchanged derivatives within a rigid band model, we find that the
injected charges in Mn exchanged vanadium oxide nanoscrolls are pinned.
A low-energy electronic excitation associated with the pinned carriers appears
in the far infrared and persists at low temperature, suggesting that the
nanoscrolls are weak metals in their bulk form, dominated by inhomogeneous
charge disproportionation and Madelung energy effects.Comment: 4 figure
Gravitational lensing effects on sub-millimetre galaxy counts
We study the effects on the number counts of sub-millimetre galaxies due to
gravitational lensing. We explore the effects on the magnification cross
section due to halo density profiles, ellipticity and cosmological parameter
(the power-spectrum normalisation ). We show that the ellipticity
does not strongly affect the magnification cross section in gravitational
lensing while the halo radial profiles do. Since the baryonic cooling effect is
stronger in galaxies than clusters, galactic haloes are more concentrated. In
light of this, a new scenario of two halo population model is explored where
galaxies are modeled as a singular isothermal sphere profile and clusters as a
Navarro, Frenk and White (NFW) profile. We find the transition mass between the
two has modest effects on the lensing probability. The cosmological parameter
alters the abundance of haloes and therefore affects our results.
Compared with other methods, our model is simpler and more realistic. The
conclusions of previous works is confirm that gravitational lensing is a
natural explanation for the number count excess at the bright end.Comment: 10 pages, 10 figures, accepted by MNRA
Evolution of Magnetism in Single-Crystal Honeycomb Iridates
We report the successful synthesis of single-crystals of the layered iridate,
(NaLi)IrO, , and a thorough study of
its structural, magnetic, thermal and transport properties. The new compound
allows a controlled interpolation between NaIrO and LiIrO,
while maintaing the novel quantum magnetism of the honeycomb Ir planes.
The measured phase diagram demonstrates a dramatic suppression of the N\'eel
temperature, , at intermediate suggesting that the magnetic order in
NaIrO and LiIrO are distinct, and that at , the
compound is close to a magnetically disordered phase that has been sought after
in NaIrO and LiIrO. By analyzing our magnetic data with a
simple theoretical model we also show that the trigonal splitting, on the
Ir ions changes sign from NaIrO and LiIrO, and the
honeycomb iridates are in the strong spin-orbit coupling regime, controlled by
\jeff=1/2 moments.Comment: updated version with more dat
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