8 research outputs found
Superfluidity and magnetism in multicomponent ultracold fermions
We study the interplay between superfluidity and magnetism in a
multicomponent gas of ultracold fermions. Ward-Takahashi identities constrain
possible mean-field states describing order parameters for both pairing and
magnetization. The structure of global phase diagrams arises from competition
among these states as functions of anisotropies in chemical potential, density,
or interactions. They exhibit first and second order phase transition as well
as multicritical points, metastability regions, and phase separation. We
comment on experimental signatures in ultracold atoms.Comment: 4 pages, 3 figure
Symmetry analysis of crystalline spin textures in dipolar spinor condensates
We study periodic crystalline spin textures in spinor condensates with
dipolar interactions via a systematic symmetry analysis of the low-energy
effective theory. By considering symmetry operations which combine real and
spin space operations, we classify symmetry groups consistent with non-trivial
experimental and theoretical constraints. Minimizing the energy within each
symmetry class allows us to explore possible ground states.Comment: 19 pages, 4 figure
Neutral skyrmion configurations in the low-energy effective theory of spinor condensate ferromagnets
We study the low-energy effective theory of spinor condensate ferromagnets
for the superfluid velocity and magnetization degrees of freedom. This
effective theory describes the competition between spin stiffness and a
long-ranged interaction between skyrmions, topological objects familiar from
the theory of ordinary ferromagnets. We find exact solutions to the non-linear
equations of motion describing neutral configurations of skyrmions and
anti-skyrmions. These analytical solutions provide a simple physical picture
for the origin of crystalline magnetic order in spinor condensate ferromagnets
with dipolar interactions. We also point out the connections to effective
theories for quantum Hall ferromagnets.Comment: 13 pages, 7 figure
Probing quantum and thermal noise in an interacting many-body system
The probabilistic character of the measurement process is one of the most
puzzling and fascinating aspects of quantum mechanics. In many-body systems
quantum mechanical noise reveals non-local correlations of the underlying
many-body states. Here, we provide a complete experimental analysis of the
shot-to-shot variations of interference fringe contrast for pairs of
independently created one-dimensional Bose condensates. Analyzing different
system sizes we observe the crossover from thermal to quantum noise, reflected
in a characteristic change in the distribution functions from Poissonian to
Gumbel-type, in excellent agreement with theoretical predictions based on the
Luttinger liquid formalism. We present the first experimental observation of
quasi long-range order in one-dimensional atomic condensates, which is a
hallmark of quantum fluctuations in one-dimensional systems. Furthermore, our
experiments constitute the first analysis of the full distribution of quantum
noise in an interacting many-body system
The physics of dipolar bosonic quantum gases
This article reviews the recent theoretical and experimental advances in the
study of ultracold gases made of bosonic particles interacting via the
long-range, anisotropic dipole-dipole interaction, in addition to the
short-range and isotropic contact interaction usually at work in ultracold
gases. The specific properties emerging from the dipolar interaction are
emphasized, from the mean-field regime valid for dilute Bose-Einstein
condensates, to the strongly correlated regimes reached for dipolar bosons in
optical lattices.Comment: Review article, 71 pages, 35 figures, 350 references. Submitted to
Reports on Progress in Physic