Biomedical subjects

F S Cataliotti

Publications and source records attributed to F S Cataliotti.

6 recordsLinked to original sources

PubMed2003

Optically induced lensing effect on a Bose-Einstein condensate expanding in a moving lattice.

We report the experimental observation of a lensing effect on a Bose-Einstein condensate expanding in a moving 1D optical lattice. The effect of the periodic potential can be described by an effective mass dependent on the condensate quasimomentum. By changing the velocity of the atoms in the frame of the optical lattice, we induce a focusing of the condensate along the lattice direction. The experimental results are compared with the numerical predictions of an effective 1D theoretical model. In addition, a precise band spectroscopy of the system is carried out by looking at the real-space propagation of the atomic wave packet in the optical lattice.

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PubMed2003

Collective excitations of a trapped Bose-Einstein condensate in the presence of a 1D optical lattice.

We study low-lying collective modes of an elongated 87Rb condensate produced in a 3D magnetic harmonic trap with the addition of a 1D periodic potential which is provided by a laser standing wave along the axial direction. While the transverse breathing mode remains unperturbed, quadrupole and dipole oscillations along the optical lattice are strongly modified. Precise measurements of the collective mode frequencies at different heights of the optical barriers provide a stringent test of the theoretical model recently introduced [M. Krämer, Phys. Rev. Lett. 88, 180404 (2002)]].

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PubMed2001

Expansion of a coherent array of Bose-Einstein condensates.

We investigate the properties of a coherent array containing about 200 Bose-Einstein condensates produced in a far detuned 1D optical lattice. The density profile of the gas, imaged after releasing the trap, provides information about the coherence of the ground-state wave function. The measured atomic distribution is characterized by interference peaks. The time evolution of the peaks, their relative population, as well as the radial size of the expanding cloud are in good agreement with the predictions of theory. The 2D nature of the trapped condensates and the conditions required to observe the effects of coherence are also discussed.

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PubMed2001

Superresolution of pulsed multiphoton Raman transitions.

We have investigated higher order multiphoton Raman resonances with two pulsed optical frequencies. Multiphoton transfer with up to 50 photons is observed with milliwatts of laser power. We demonstrate that the spectral width of the multiphoton resonances can be far below the Fourier transform linewidth of the driving optical pulses. The functional dependence of the transition linewidth on the number of exchanged photons is found to vary with the pulse shape. Our experiment is performed with laser-cooled rubidium atoms confined in a CO2-laser optical dipole trap.

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PubMed2001

Josephson junction arrays with Bose-Einstein condensates.

We report on the direct observation of an oscillating atomic current in a one-dimensional array of Josephson junctions realized with an atomic Bose-Einstein condensate. The array is created by a laser standing wave, with the condensates trapped in the valleys of the periodic potential and weakly coupled by the interwell barriers. The coherence of multiple tunneling between adjacent wells is continuously probed by atomic interference. The square of the small-amplitude oscillation frequency is proportional to the microscopic tunneling rate of each condensate through the barriers and provides a direct measurement of the Josephson critical current as a function of the intermediate barrier heights. Our superfluid array may allow investigation of phenomena so far inaccessible to superconducting Josephson junctions and lays a bridge between the condensate dynamics and the physics of discrete nonlinear media.

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PubMed2001

Superfluid and dissipative dynamics of a Bose-Einstein condensate in a periodic optical potential.

We create Bose-Einstein condensates of 87Rb in a static magnetic trap with a superimposed blue-detuned 1D optical lattice. By displacing the magnetic trap center we are able to control the condensate evolution. We observe a change in the frequency of the center-of-mass oscillation in the harmonic trapping potential, in analogy with an increase in effective mass. For fluid velocities greater than a local speed of sound, we observe the onset of dissipative processes up to full removal of the superfluid component. A parallel simulation study visualizes the dynamics of the Bose-Einstein condensate and accounts for the main features of the observed behavior.

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