Observation of Massless and Massive Collective Excitations with Faraday Patterns in a Two-Component Superfluid.

We report on the experimental measurement of the dispersion relation of the density and spin collective excitation modes in an elongated two-component superfluid of ultracold bosonic atoms. Our parametric spectroscopic technique is based on the external modulation of the transverse confinement frequency, leading to the formation of density and spin Faraday waves. We show that the application of a coherent coupling between the two components reduces the phase symmetry and gives a finite mass to the spin modes.

An adaptable two-lens high-resolution objective for single-site resolved imaging of atoms in optical lattices.

In this paper, we present a high-resolution, simple, and versatile imaging system for single-site resolved imaging of atoms in optical lattices. The system, which relies on an adaptable infinite conjugate two-lens design, has a numerical aperture of 0.52, which can in the ideal case be further extended to 0.57. It is optimized for imaging on the sodium D2-line but allows us to tune the objective's diffraction limited performance between 400 nm and 1000 nm by changing the distance between the two lenses. Furthermore, the objective is designed to be integrated into a typical atomic physics vacuum apparatus where the operating distance can be large (>20 mm) and diffraction limited performance still needs to be achieved when imaging through thick vacuum windows (6 mm to 10 mm). Imaging gold nanoparticles, using a wavelength of 589 nm which corresponds to the D2-line of sodium atoms, we measure diffraction limited performance and a resolution corresponding to an Airy radius of less than 0.7 µm, enabling potential single-site resolution in the commonly used 532 nm optical lattice spacing.

Universality of the three-body parameter for Efimov states in ultracold cesium.

We report on the observation of triatomic Efimov resonances in an ultracold gas of cesium atoms. Exploiting the wide tunability of interactions resulting from three broad Feshbach resonances in the same spin channel, we measure magnetic-field dependent three-body recombination loss. The positions of the loss resonances yield corresponding values for the three-body parameter, which in universal few-body physics is required to describe three-body phenomena and, in particular, to fix the spectrum of Efimov states. Our observations show a robust universal behavior with a three-body parameter that stays essentially constant.

Time-resolved measurement of Landau-Zener tunneling in periodic potentials.

We report time-resolved measurements of Landau-Zener tunneling of Bose-Einstein condensates in accelerated optical lattices, clearly resolving the steplike time dependence of the band populations. Using different experimental protocols we were able to measure the tunneling probability both in the adiabatic and in the diabatic bases of the system. We also experimentally determine the contribution of the momentum width of the Bose condensates to the temporal width of the tunneling steps and discuss the implications for measuring the jump time in the Landau-Zener problem.

Observation of photon-assisted tunneling in optical lattices.

We have observed tunneling suppression and photon-assisted tunneling of Bose-Einstein condensates in an optical lattice subjected to a constant force plus a sinusoidal shaking. For a sufficiently large constant force, the ground energy levels of the lattice are shifted out of resonance and tunneling is suppressed; when the shaking is switched on, the levels are coupled by low-frequency photons and tunneling resumes. Our results agree well with theoretical predictions and demonstrate the usefulness of optical lattices for studying solid-state phenomena.

Resonantly enhanced tunneling of Bose-Einstein condensates in periodic potentials.

We report on measurements of resonantly enhanced tunneling of Bose-Einstein condensates loaded into an optical lattice. By controlling the initial conditions of our system we were able to observe resonant tunneling in the ground and the first two excited states of the lattice wells. We also investigated the effect of the intrinsic nonlinearity of the condensate on the tunneling resonances.

Dynamical control of matter-wave tunneling in periodic potentials.

We report on measurements of dynamical suppression of interwell tunneling of a Bose-Einstein condensate (BEC) in a strongly driven optical lattice. The strong driving is a sinusoidal shaking of the lattice corresponding to a time-varying linear potential, and the tunneling is measured by letting the BEC freely expand in the lattice. The measured tunneling rate is reduced and, for certain values of the shaking parameter, completely suppressed. Our results are in excellent agreement with theoretical predictions. Furthermore, we have verified that, in general, the strong shaking does not destroy the phase coherence of the BEC, opening up the possibility of realizing quantum phase transitions by using the shaking strength as the control parameter.

[An unusual site of bleeding from esophageal varices]. / Un'insolita sede di sanguinamento da varici esofagee.

A case of massive upper gastrointestinal haemorrhage from proximal esophageal varices is reported. Upper esophageal varices occur rarely, and serve as collaterals in conditions of superior vena cava obstruction. In our patient, cervical esophageal varices were associated with portal hypertension due to occult liver cirrhosis. As the diagnosis was made at autopsy, this case serves to stress the importance of a through examination of the cervical portion of the esophagus during routine endoscopy.