1,737 research outputs found
Magnetic moment suppression in Ba3CoRu2O9: hybridization effect
An unusual orbital state was recently proposed to explain the magnetic and
transport properties of BaCoRuO [Phys. Rev. B. {\bf 85}, 041201
(2012)]. We show that this state contradicts to the first Hund's rule and does
not realize in the system under consideration because of a too small
crystal-field splitting in the shell. A strong suppression of the
local magnetic moment in BaCoRuO is attributed to a strong
hybridization between the Ru 4 and O 2 states.Comment: 5 pages, 5 figure
How does an interacting many-body system tunnel through a potential barrier to open space?
The tunneling process in a many-body system is a phenomenon which lies at the
very heart of quantum mechanics. It appears in nature in the form of
alpha-decay, fusion and fission in nuclear physics, photoassociation and
photodissociation in biology and chemistry. A detailed theoretical description
of the decay process in these systems is a very cumbersome problem, either
because of very complicated or even unknown interparticle interactions or due
to a large number of constitutent particles. In this work, we theoretically
study the phenomenon of quantum many-body tunneling in a more transparent and
controllable physical system, in an ultracold atomic gas. We analyze a full,
numerically exact many-body solution of the Schr\"odinger equation of a
one-dimensional system with repulsive interactions tunneling to open space. We
show how the emitted particles dissociate or fragment from the trapped and
coherent source of bosons: the overall many-particle decay process is a quantum
interference of single-particle tunneling processes emerging from sources with
different particle numbers taking place simultaneously. The close relation to
atom lasers and ionization processes allows us to unveil the great relevance of
many-body correlations between the emitted and trapped fractions of the
wavefunction in the respective processes.Comment: 18 pages, 4 figures (7 pages, 2 figures supplementary information
Jahn-Teller distortions and charge, orbital and magnetic orders in NaMn7O12
With the use of the band structure calculations we demonstrate that
previously reported [Nat. Materials {\bf 3}, 48 (2004)] experimental crystal
and magnetic structures for NaMnO are inconsistent with each other.
The optimization of the crystal lattice allows us to predict a new crystal
structure for the low temperature phase, which is qualitatively different from
the one presented before. The AFM-CE type of the magnetic order stabilizes the
structure with the elongated, not compressed MnO octahedra,
striking NaMnO out of the list of the anomalous Jahn-Teller systems.
The orbital correlations were shown to exist even in the cubic phase, while the
charge order appears only in the low temperature distorted phase.Comment: 5 page
Time-dependent multi-orbital mean-field for fragmented Bose-Einstein condensates
The evolution of Bose-Einstein condensates is usually described by the famous
time-dependent Gross-Pitaevskii equation, which assumes all bosons to reside in
a single time-dependent orbital. In the present work we address the evolution
of fragmented condensates, for which two (or more) orbitals are occupied, and
derive a corresponding time-dependent multi-orbital mean-field theory. We call
our theory TDMF(), where stands for the number of evolving fragments.
Working equations for a general two-body interaction between the bosons are
explicitly presented along with an illustrative numerical example.Comment: 16 pages, 1 figur
Rates of multi-partite entanglement transformations and applications in quantum networks
The theory of the asymptotic manipulation of pure bipartite quantum systems
can be considered completely understood: The rates at which bipartite entangled
states can be asymptotically transformed into each other are fully determined
by a single number each, the respective entanglement entropy. In the
multi-partite setting, similar questions of the optimally achievable rates of
transforming one pure state into another are notoriously open. This seems
particularly unfortunate in the light of the revived interest in such questions
due to the perspective of experimentally realizing multi-partite quantum
networks. In this work, we report substantial progress by deriving surprisingly
simple upper and lower bounds on the rates that can be achieved in asymptotic
multi-partite entanglement transformations. These bounds are based on ideas of
entanglement combing and state merging. We identify cases where the bounds
coincide and hence provide the exact rates. As an example, we bound rates at
which resource states for the cryptographic scheme of quantum secret sharing
can be distilled from arbitrary pure tripartite quantum states, providing
further scope for quantum internet applications beyond point-to-point.Comment: 4+7 pages, 1 figure, v2 is significantly extended in its results and
presents a general statement providing bounds for achievable asymptotic rates
for an arbitrary number of partie
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