2,525 research outputs found
Achieving one-dimensionality with attractive fermions
In this article we discuss the accuracy of effective one-dimensional theories
used to describe the behavior of ultracold atomic ensembles confined in quantum
wires by a harmonic trap. We derive within a fully many-body approach the
effective Hamiltonian describing this class of systems and we calculate the
beyond-mean field corrections to the energy of the ground state arising from
virtual transitions towards excited state of the confining potential. We find
that, due to the Pauli principle, effective finite-range corrections are one of
magnitude larger than effective three-body interactions.By comparing to exact
solutions of the purely 1D problem, we conclude that a 1D effective theory
provides a good description of the ground state of the system for a rather
large range of interaction parameters
Emerging roles of 3D-culture systems in tackling tumor drug resistance
Drug resistance that affects patients universally is a major challenge in cancer therapy. The development of drug resistance in cancer cells is a multifactor event, and its process involves numerous mechanisms that allow these cells to evade the effect of treatments. As a result, the need to understand the molecular mechanisms underlying cancer drug sensitivity is imperative. Traditional 2D cell culture systems have been utilized to study drug resistance, but they often fail to mimic the 3D milieu and the architecture of real tissues and cell-cell interactions. As a result of this, 3D cell culture systems are now considered a comprehensive model to study drug resistance in vitro. Cancer cells exhibit an in vivo behavior when grown in a three-dimensional environment and react to therapy more physiologically. In this review, we discuss the relevance of main 3D culture systems in the study of potential approaches to overcome drug resistance and in the identification of personalized drug targets with the aim of developing patient-specific treatment strategies that can be put in place when resistance emerges
Interaction quantum quenches in the one-dimensional Fermi-Hubbard model with spin imbalance
Using the time-dependent density matrix renormalization group method and
exact diagonalization, we study the non-equilibrium dynamics of the
one-dimensional Fermi-Hubbard model following a quantum quench or a ramp of the
onsite interaction strength. For quenches from the non-interacting to the
attractive regime, we investigate the dynamical emergence of
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) correlations, which at finite spin
polarizations are the dominant two-body correlations in the ground state, and
their signatures in the pair quasi-momentum distribution function. We observe
that the post-quench double occupancy exhibits a maximum as the interaction
strength becomes of the order of the bandwidth. Finally, we study quenches and
ramps from attractive to repulsive interactions, which imprint FFLO
correlations onto repulsively bound pairs. We show that a quite short ramp time
is sufficient to wipe out the characteristic FFLO features in the post-quench
pair momentum distribution functions.Comment: 13 pages, 15 figures, minor revisions, version as publishe
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
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