436 research outputs found
Time-dependent currents of 1D bosons in an optical lattice
We analyse the time-dependence of currents in a 1D Bose gas in an optical
lattice. For a 1D system, the stability of currents induced by accelerating the
lattice exhibits a broad crossover as a function of the magnitude of the
acceleration, and the strength of the inter-particle interactions. This differs
markedly from mean-field results in higher dimensions. Using the infinite Time
Evolving Block Decimation algorithm, we characterise this crossover by making
quantitative predictions for the time-dependent behaviour of the currents and
their decay rate. We also compute the time-dependence of quasi-condensate
fractions which can be measured directly in experiments. We compare our results
to calculations based on phase-slip methods, finding agreement with the scaling
as the particle density increases, but with significant deviations near unit
filling.Comment: 19 pages, 10 figure
Trimer liquids and crystals of polar molecules in coupled wires
We investigate the pairing and crystalline instabilities of bosonic and
fermionic polar molecules confined to a ladder geometry. By means of analytical
and quasi-exact numerical techniques, we show that gases of composite molecular
dimers as well as trimers can be stabilized as a function of the density
difference between the wires. A shallow optical lattice can pin both liquids,
realizing crystals of composite bosons or fermions. We show that these exotic
quantum phases should be realizable under current experimental conditions in
finite-size confining potentials.Comment: 5 pages, 3 figures plus additional material; Accepted for publication
in Phys. Rev. Let
Strongly correlated gases of Rydberg-dressed atoms: quantum and classical dynamics
We discuss techniques to generate long-range interactions in a gas of
groundstate alkali atoms, by weakly admixing excited Rydberg states with laser
light. This provides a tool to engineer strongly correlated phases with reduced
decoherence from inelastic collisions and spontaneous emission. As an
illustration, we discuss the quantum phases of dressed atoms with dipole-dipole
interactions confined in a harmonic potential, as relevant to experiments. We
show that residual spontaneous emission from the Rydberg state acts as a
heating mechanism, leading to a quantum-classical crossover.Comment: 4 pages, 4 figure
A superfluid-droplet crystal and a free-space supersolid in a dipole-blockaded gas
A novel supersolid phase is predicted for an ensemble of Rydberg atoms in the
dipole-blockade regime, interacting via a repulsive dipolar potential
"softened" at short distances. Using exact numerical techniques, we study the
low temperature phase diagram of this system, and observe an intriguing phase
consisting of a crystal of mesoscopic superfluid droplets. At low temperature,
phase coherence throughout the whole system, and the ensuing bulk
superfluidity, are established through tunnelling of identical particles
between neighbouring droplets.Comment: 4 pages, 4 figure
Bose-Einstein Condensation of Erbium
We report on the achievement of Bose-Einstein condensation of erbium atoms
and on the observation of magnetic Feshbach resonances at low magnetic field.
By means of evaporative cooling in an optical dipole trap, we produce pure
condensates of Er, containing up to atoms. Feshbach
spectroscopy reveals an extraordinary rich loss spectrum with six loss
resonances already in a narrow magnetic-field range up to 3 G. Finally, we
demonstrate the application of a low-field Feshbach resonance to produce a
tunable dipolar Bose-Einstein condensate and we observe its characteristic
d-wave collapse.Comment: 4 pages, 3 figure
The Leonid meteor shower 1996-2002: Results from forward-scatter radio observations
Results from the observations of the Leonid meteor shower in 1996-2002 by the BLM (Bologna-Lecce-Modra)
forward-scatter radio system for meteor observation carried out along two baselines, Bologna-Lecce (Italy)and
Bologna-Modra (Slovakia), are presented and discussed. The activity curves of long-duration echoes (≥ 8 s)and their variations indicate multiple peak activity which are attributed to filamentary structure of the stream. The mass distribution exponents in the period of the shower maximum shows significant changes in individual years, with a high contribution of larger particles chiefly in 1998
- …