2,368 research outputs found
Attractive Fermi gases with unequal spin populations in highly elongated traps
We investigate two-component attractive Fermi gases with imbalanced spin
populations in trapped one dimensional configurations. The ground state
properties are determined within local density approximation, starting from the
exact Bethe-ansatz equations for the homogeneous case. We predict that the
atoms are distributed according to a two-shell structure: a partially polarized
phase in the center of the trap and either a fully paired or a fully polarized
phase in the wings. The partially polarized core is expected to be a superfluid
of the FFLO type. The size of the cloud as well as the critical spin
polarization needed to suppress the fully paired shell, are calculated as a
function of the coupling strength.Comment: Final accepted versio
Landau-Zener sweeps and sudden quenches in coupled Bose-Hubbard chains
We simulate numerically the dynamics of strongly correlated bosons in a
two-leg ladder subject to a time-dependent energy bias between the two chains.
When all atoms are initially in the leg with higher energy, we find a drastic
reduction of the inter-chain particle transfer for slow linear sweeps, in
quantitative agreement with recent experiments. This effect is preceded by a
rapid broadening of the quasi-momentum distribution of atoms, signaling the
presence of a bath of low-energy excitations in the chains. We further
investigate the scenario of quantum quenches to fixed values of the energy
bias. We find that for large enough density the momentum distribution relaxes
to that of an equilibrium thermal state with the same energy.Comment: 6 pages, 4 figure
Long-time behavior of the momentum distribution during the sudden expansion of a spin-imbalanced Fermi gas in one dimension
We study the sudden expansion of spin-imbalanced ultracold lattice fermions
with attractive interactions in one dimension after turning off the
longitudinal confining potential. We show that the momentum distribution
functions of majority and minority fermions approach stationary values quickly
due to a quantum distillation mechanism that results in a spatial separation of
pairs and majority fermions. As a consequence, Fulde-Ferrell-Larkin-Ovchinnikov
(FFLO) correlations are lost during the expansion. Furthermore, we argue that
the shape of the stationary momentum distribution functions can be understood
by relating them to the integrals of motion in this integrable quantum system.
We discuss our results in the context of proposals to observe FFLO
correlations, related to recent experiments by Liao et al., Nature 467, 567
(2010).Comment: 8 pages including supplementary material, 9 eps figures, revised
version as published, some text moved to the supplemental materia
Dimer, trimer and FFLO liquids in mass- and spin-imbalanced trapped binary mixtures in one dimension
We present a systematic investigation of attractive binary mixtures in
presence of both spin- and mass-imbalance in one dimensional setups described
by the Hubbard model. After discussing typical cold atomic experimental
realizations and the relation between microscopic and effective parameters, we
study several many-body features of trapped Fermi-Fermi and Bose-Bose mixtures
such as density profiles, momentum distributions and correlation functions by
means of numerical density-matrix-renormalization-group and Quantum Monte Carlo
simulations. In particular, we focus on the stability of
Fulde-Ferrell-Larkin-Ovchinnikov, dimer and trimer fluids in inhomogeneous
situations, as typically realized in cold gas experiments due to the harmonic
confinement. We finally consider possible experimental signatures of these
phases both in the presence of a finite polarization and of a finite
temperature.Comment: 19 pages, 25 figure
Learning from the italian experience during covid-19 pandemic waves: Be prepared and mind some crucial aspects
COVID-19 pandemic has rapidly spread worldwide causing a serious challenge to the global medical community. Italy was struck hard during the first wave earlier this year and several weaknesses as well as general unpreparedness of the national healthcare system were acknowledged. Learning essential lessons from the past, we realized how implementing contingency response measures, human resources and social dynamics could have changed the outcome if promptly adopted. This review translates the previous experience into strategic actions that has to be considered when developing appropriate national and regional operational plans to respond to a pandemic
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