arXiv subjects

E. Arimondo

Publications and source records attributed to E. Arimondo.

At least 55 records · Page 3Linked to original sources

arXiv2004

Atomic gallium laser spectroscopy with violet/blue diode lasers

We describe the operation of two GaN-based diode lasers for the laser spectroscopy of gallium at 403 nm and 417 nm. Their use in an external cavity configuration enabled the investigation of absorption spectroscopy in a gallium hollow cathode. We have analyzed the Doppler broadened profiles accounting for hyperfine and isotope structure and extracting both the temperature and densities of the neutral atomic sample produced in the glow discharge. We have also built a setup to produce a thermal atomic beam of gallium. Using the GaN-based diode lasers we have studied the laser induced fluorescence and hyperfine resolved spectra of gallium.

physics.atom-ph↗

arXiv2004

Stability of small amplitude normal modes of a Bose-Einstein condensate with a singly quantized vortex confined in an optical lattice

We study the dynamics of a BEC with a singly quantized vortex, placed in the combined potential of a 1-D (2-D) optical lattice and an axi-symmetric harmonic trap. A time-dependent variational Lagrangian analysis shows that an optical lattice helps to stabilize the vortex which in absence of the optical lattice is unstable. We find that the normal modes are stable only if the depth of the optical potential is more than a certain critical value. This critical value of the optical potential depends on the interaction parameter.In general higher the interaction parameter,lower the value of the optical potential required to stabilize the vortex. The BEC with the singly quantized vortex is found to be relatively more unstable in a 2-D optical lattice compared to a 1-D optical lattice.

cond-mat.stat-mech↗

arXiv2003

Rotational bosonic current in a quasi-condensate confined in an optical toroidal trap

We investigate the possibility of inducing a bosonic current which is rotational in a pseudo 1D quasi-condensate confined in an optical toroidal trap. The stability of such a current is also analyzed using hydrodynamics approach. We find that such a current is uniform when the circular symmetry is preserved and energetically stable when the modes of elementary excitations are restricted to one dimension. This scheme allows to distinguish between a quasi and a true condensate by measuring the rotational spectra of the sample.

cond-mat.stat-mech↗

arXiv2003

Instabilities of a Bose-Einstein condensate in a periodic potential: an experimental investigation

By accelerating a Bose-Einstein condensate in a controlled way across the edge of the Brillouin zone of a 1D optical lattice, we investigate the stability of the condensate in the vicinity of the zone edge. Through an analysis of the visibility of the interference pattern after a time-of-flight and the widths of the interference peaks, we characterize the onset of instability as the acceleration of the lattice is decreased. We briefly discuss the significance of our results with respect to recent theoretical work.

cond-mat↗

arXiv2003

Asymmetric Landau-Zener tunneling in a periodic potential

Using a simple model for nonlinear Landau-Zener tunneling between two energy bands of a Bose-Einstein condensate in a periodic potential, we find that the tunneling rates for the two directions of tunneling are not the same. Tunneling from the ground state to the excited state is enhanced by the nonlinearity, whereas in the opposite direction it is suppressed. These findings are confirmed by numerical simulations of the condensate dynamics. Measuring the tunneling rates for a condensate of rubidium atoms in an optical lattice, we have found experimental evidence for this asymmetry.

cond-mat.soft↗

arXiv2002

Hitting a BEC with a comb: Evolution of interference patterns inside a magnetic trap

We study the evolution inside a harmonic trap of Bose-Einstein condensates released from the periodic potential of an optical lattice. After a time-of-flight, harmonic motion of the interference peaks is observed as well as a breathing motion in the direction perpendicular to the optical lattice. We interpret these results in terms of a simple physical model and discuss the possibility of more detailed studies of such a system.

cond-mat.soft↗

arXiv2002

Dynamics and phase evolution of Bose-Einstein condensates in one-dimensional optical lattices

We report experimental results on the dynamics and phase evolution of Bose-Einstein condensates in 1D optical lattices. The dynamical behaviour is studied by adiabatically loading the condensate into the lattice and subsequently switching off the magnetic trap. In this case, the condensate is free to expand inside the periodic structure of the optical lattice. The phase evolution of the condensate, on the other hand, can be studied by non-adiabatically switching on the periodic potential. We observe decays and revivals of the interference pattern after a time-of-flight.

cond-mat↗

arXiv2002

Ultracold atoms and Bose-Einstein condensates in optical lattices

For ultracold and Bose-condensed atoms contained in periodic optical potential wells the quantized nature of their motion is clearly visible. The motion of the atomic wavepacket can also be accurately controlled. For those systems the long-range character of the atomic interaction and of the external potential play a key role in the quantum mechanical evolution. The basic facets of the experimental and theoretical research for atoms within optical lattice structures will be reviewed.

cond-mat↗

arXiv2002

Excitation and damping of collective modes of a Bose-Einstein condensate in a one-dimensional lattice

The mode structure of a Bose-Einstein condensate non-adiabatically loaded into a one-dimensional optical lattice is studied by analyzing the visibility of the interference pattern as well as the radial profile of the condensate after a time-of-flight. A simple model is proposed that predicts the short-time decrease of the visibility as a function of the condensate parameters. In the radial direction, heavily damped oscillations are observed, as well as an increase in the condensate temperature. These findings are interpreted as a re-thermalization due to dissipation of the initial condensate excitations into high-lying modes.

cond-mat.soft↗

arXiv2002

Photoionization of ultracold and Bose-Einstein condensed Rb atoms

Photoionization of a cold atomic sample offers intriguing possibilities to observe collective effects at extremely low temperatures. Irradiation of a rubidium condensate and of cold rubidium atoms within a magneto-optical trap with laser pulses ionizing through 1-photon and 2-photon absorption processes has been performed. Losses and modifications in the density profile of the remaining trapped cold cloud or the remaining condensate sample have been examined as function of the ionizing laser parameters. Ionization cross-sections were measured for atoms in a MOT, while in magnetic traps losses larger than those expected for ionization process were measured.

physics.atom-ph↗

arXiv2002

Free expansion of a Bose-Einstein condensate in a 1D optical lattice

We have experimentally investigated the free expansion of a Bose-Einstein condensate in an array of two-dimensional traps created by a one-dimensional optical lattice. If the condensate held in a magnetic trap is loaded adiabatically into the lattice, the increase in chemical potential due to the additional periodic potential is reflected in the expansion of the condensate after switching off the magnetic trap. We have calculated the chemical potential from measurements of the transverse expansion of the condensate as a function of the lattice parameters.

cond-mat.soft↗

arXiv2002

Experimental properties of Bose-Einstein condensates in 1D optical lattices: Bloch oscillations, Landau-Zener tunneling and mean-field effects

We report experimental results on the properties of Bose-Einstein condensates in 1D optical lattices. By accelerating the lattice, we observed Bloch oscillations of the condensate in the lowest band, as well as Landau-Zener (L-Z) tunneling into higher bands when the lattice depth was reduced and/or the acceleration of the lattice was increased. The dependence of the L-Z tunneling rate on the condensate density was then related to mean-field effects modifying the effective potential acting on the condensate, yielding good agreement with recent theoretical work. We also present several methods for measuring the lattice depth and discuss the effects of the micromotion in the TOP-trap on our experimental results.

cond-mat.soft↗

arXiv2001

Correlation functions for a Bose-Einstein condensate in the Bogoliubov approximation

In this article we introduce a differential equation for the first order correlation function $G^{(1)}$ of a Bose-Einstein condensate at T=0. The Bogoliubov approximation is used. Our approach points out directly the dependence on the physical parameters. Furthermore it suggests a numerical method to calculate $G^{(1)}$ without solving an eigenvector problem. The $G^{(1)}$ equation is generalized to the case of non zero temperature.

cond-mat↗

arXiv2001

Bloch oscillations and mean-field effects of Bose-Einstein condensates in 1-D optical lattices

We have loaded Bose-Einstein condensates into one-dimensional, off-resonant optical lattices and accelerated them by chirping the frequency difference between the two lattice beams. For small values of the lattice well-depth, Bloch oscillations were observed. Reducing the potential depth further, Landau-Zener tunneling out of the lowest lattice band, leading to a breakdown of the oscillations, was also studied and used as a probe for the effective potential resulting from mean-field interactions as predicted by Choi and Niu [Phys. Rev. Lett. {\bf 82}, 2022 (1999)]. The effective potential was measured for various condensate densities and trap geometries, yielding good qualitative agreement with theoretical calculations.

cond-mat.soft↗

arXiv2001

Coherent acceleration and Landau-Zener tunneling of Bose-Einstein condensates in 1-D optical lattices

We have loaded Bose-Einstein condensates into one-dimensional, off-resonant optical lattices and accelerated them by chirping the frequency difference between the two lattice beams. For small values of the lattice well-depth, Bloch oscillations were observed. Landau-Zener tunneling out of the lowest lattice band, leading to a breakdown of the oscillations, was also studied. In order to allow in-trap measurements of these phenomena, we dynamically compensated for the intrinsic micromotion of the atoms in our time-orbiting potential trap.

cond-mat↗

arXiv2001

Slow light in three-level cold atoms: a numerical analysis

We investigate theoretically the slow group velocity of a pulse probe laser propagating through a cold sample and interacting with atoms in a three-level $Λ$ configuration having losses towards external states. The EIT phenomenon produces very small group velocities for the probe pulse in presence of a strong coupling field even in presence of the population losses, as in an open three-level system. The group velocity and the transmission of the pulses are examined numerically as functions of several parameters, the adiabatic transfer, the loss rate, the modification of the atomic velocity produced within the cold sample. The conditions for a more efficient pulse transmission through the cold atomic sample are specified.

quant-ph↗

arXiv2001

Enhanced absorption Hanle effect on the Fg=F->Fe=F+1 closed transitions

We analyse the Hanle effect on a closed $F_g\to F_e=F_g+1$ transition. Two configurations are examined, for linear- and circular-polarized laser radiation, with the applied magnetic field collinear to the laser light wavevector. We describe the peculiarities of the Hanle signal for linearly-polarized laser excitation, characterized by narrow bright resonances at low laser intensities. The mechanism behind this effect is identified, and numerical solutions for the optical Bloch equations are presented for different transitions.

quant-ph↗

arXiv2000

Atomic micromotion and geometric forces in a triaxial magnetic trap

Non-adiabatic motion of Bose-Einstein condensates of rubidium atoms arising from the dynamical nature of a time-orbiting-potential (TOP) trap was observed experimentally. The orbital micromotion of the condensate in velocity space at the frequency of the rotating bias field of the TOP was detected by a time-of-flight method. A dependence of the equilibrium position of the atoms on the sense of rotation of the bias field was observed. We have compared our experimental findings with numerical simulations. The nonadiabatic following of the atomic spin in the trap rotating magnetic field produces geometric forces acting on the trapped atoms.

physics.atom-ph↗