6,120 research outputs found
Emergence of Quintet Superfluidity in the Chain of Partially Polarized Spin-3/2 Ultracold Atom
The system of ultracold atoms with hyperfine spin might be unstable
against the formation of quintet pairs if the interaction is attractive in the
quintet channel. We have investigated the behavior of correlation functions in
a model including only s-wave interactions at quarter filling by large-scale
density-matrix renormalization-group simulations. We show that the correlations
of quintet pairs become quasi-long-ranged, when the system is partially
polarized, leading to the emergence of various mixed superfluid phases in which
BCS-like pairs carrying different magnetic moment coexist.Comment: 4 pages, 4 figures; significantly rewritten compared to the first
versio
Crop ontology in support of conservation and use of banana genetic resources
Poster presented at Workshop on Crop Ontology and Phenotyping Data Interoperability. Montpellier (France), 31 Mar-4 Apr 201
Model-Checking with Edge-Valued Decision Diagrams
We describe an algebra of Edge-Valued Decision Diagrams (EVMDDs) to encode arithmetic functions and its implementation in a model checking library along with state-of-the-art algorithms for building the transition relation and the state space of discrete state systems. We provide efficient algorithms for manipulating EVMDDs and give upper bounds of the theoretical time complexity of these algorithms for all basic arithmetic and relational operators. We also demonstrate that the time complexity of the generic recursive algorithm for applying a binary operator on EVMDDs is no worse than that of Multi-Terminal Decision Diagrams. We have implemented a new symbolic model checker with the intention to represent in one formalism the best techniques available at the moment across a spectrum of existing tools: EVMDDs for encoding arithmetic expressions, identity-reduced MDDs for representing the transition relation, and the saturation algorithm for reachability analysis. We compare our new symbolic model checking EVMDD library with the widely used CUDD package and show that, in many cases, our tool is several orders of magnitude faster than CUDD
Zeeman effect in superconducting two-leg ladders: irrational magnetization plateaus and exceeding the Pauli limit
The effect of a parallel magnetic field on superconducting two-leg ladders is
investigated numerically. The magnetization curve displays an irrational
plateau at a magnetization equal to the hole density. Remarkably, its stability
is fundamentally connected to the existence of a well-known magnetic resonant
mode. Once the zero-field spin gap is suppressed by the field, pairs acquire a
finite momentum characteristic of a Fulde-Ferrell-Larkin-Ovchinnikov phase. In
addition, S^z=0 triplet superconducting correlations coexist with singlet ones
above the irrational plateau. This provides a simple mechanism in which the
Pauli limit is exceeded as suggested by recent experiments.Comment: 4 pages, 6 figure
Multimer formation in 1D two-component gases and trimer phase in the asymmetric attractive Hubbard model
We consider two-component one-dimensional quantum gases at special imbalanced
commensurabilities which lead to the formation of multimer (multi-particle
bound-states) as the dominant order parameter. Luttinger liquid theory supports
a mode-locking mechanism in which mass (or velocity) asymmetry is identified as
the key ingredient to stabilize such states. While the scenario is valid both
in the continuum and on a lattice, the effects of umklapp terms relevant for
densities commensurate with the lattice spacing are also mentioned. These ideas
are illustrated and confronted with the physics of the asymmetric
(mass-imbalanced) fermionic Hubbard model with attractive interactions and
densities such that a trimer phase can be stabilized. Phase diagrams are
computed using density-matrix renormalization group techniques, showing the
important role of the total density in achieving the novel phase. The effective
physics of the trimer gas is as well studied. Lastly, the effect of a parabolic
confinement and the emergence of a crystal phase of trimers are briefly
addressed. This model has connections with the physics of imbalanced
two-component fermionic gases and Bose-Fermi mixtures as the latter gives a
good phenomenological description of the numerics in the strong-coupling
regime.Comment: 17 pages, 15 figure
The quasi-periodic Bose-Hubbard model and localization in one-dimensional cold atomic gases
We compute the phase diagram of the one-dimensional Bose-Hubbard model with a
quasi-periodic potential by means of the density-matrix renormalization group
technique. This model describes the physics of cold atoms loaded in an optical
lattice in the presence of a superlattice potential whose wave length is
incommensurate with the main lattice wave length. After discussing the
conditions under which the model can be realized experimentally, the study of
the density vs. the chemical potential curves for a non-trapped system unveils
the existence of gapped phases at incommensurate densities interpreted as
incommensurate charge-density wave phases. Furthermore, a localization
transition is known to occur above a critical value of the potential depth V_2
in the case of free and hard-core bosons. We extend these results to soft-core
bosons for which the phase diagrams at fixed densities display new features
compared with the phase diagrams known for random box distribution disorder. In
particular, a direct transition from the superfluid phase to the Mott
insulating phase is found at finite V_2. Evidence for reentrances of the
superfluid phase upon increasing interactions is presented. We finally comment
on different ways to probe the emergent quantum phases and most importantly,
the existence of a critical value for the localization transition. The later
feature can be investigated by looking at the expansion of the cloud after
releasing the trap.Comment: 19 pages, 20 figure
Internal states of model isotropic granular packings. III. Elastic properties
In this third and final paper of a series, elastic properties of numerically
simulated isotropic packings of spherical beads assembled by different
procedures and subjected to a varying confining pressure P are investigated. In
addition P, which determines the stiffness of contacts by Hertz's law, elastic
moduli are chiefly sensitive to the coordination number, the possible values of
which are not necessarily correlated with the density. Comparisons of numerical
and experimental results for glass beads in the 10kPa-10MPa range reveal
similar differences between dry samples compacted by vibrations and lubricated
packings. The greater stiffness of the latter, in spite of their lower density,
can hence be attributed to a larger coordination number. Voigt and Reuss bounds
bracket bulk modulus B accurately, but simple estimation schemes fail for shear
modulus G, especially in poorly coordinated configurations under low P.
Tenuous, fragile networks respond differently to changes in load direction, as
compared to load intensity. The shear modulus, in poorly coordinated packings,
tends to vary proportionally to the degree of force indeterminacy per unit
volume. The elastic range extends to small strain intervals, in agreement with
experimental observations. The origins of nonelastic response are discussed. We
conclude that elastic moduli provide access to mechanically important
information about coordination numbers, which escape direct measurement
techniques, and indicate further perspectives.Comment: Published in Physical Review E 25 page
- …