arXiv subjects

E. de Mirandes

Publications and source records attributed to E. de Mirandes.

5 recordsLinked to original sources

arXiv2004

Atom Interferometry in a Vertical Optical Lattice

We have studied the interference of degenerate quantum gases in a vertical optical lattice. The coherence of the atoms leads to an interference pattern when the atoms are released from the lattice. This has been shown for a Bose-Einstein condensate in early experiments. Here we demonstrate that also for fermions an interference pattern can be observed provided that the momentum distribution is smaller then the recoil momentum of the lattice. Special attention is given to the role of interactions which wash out the interference pattern for a condensate but do not affect a spin polarized Fermi gas, where collisions at ultra cold temperatures are forbidden. Comparing the interference of the two quantum gases we find a clear superiority of fermions for trapped atom interferometry.

physics.atom-ph↗

arXiv2004

Collisionally Induced Transport in Periodic Potentials

We study the transport of ultra cold atoms in a tight optical lattice. For identical fermions the system is insulating under an external force while for bosonic atoms it is conducting. This reflects the different collisional properties of the particles and reveals the role of inter-particle collisions in establishing a macroscopic transport in a perfectly periodic potential. Also in the case of fermions we can induce a transport by creating a collisional regime through the addition of bosons. We investigate the transport as a function of the collisional rate and we observe a transition from a regime in which the mobility increases with increasing collisional rate to one in which it decreases. We compare our data with a theoretical model for electron transport in solids introduced by Esaki and Tsu.

cond-mat.stat-mech↗

arXiv2004

Radio Frequency Selective Addressing of Localized Particles in a Periodic Potential

We study the localization and addressability of ultra cold atoms in a combined parabolic and periodic potential. Such a potential supports the existence of localized stationary states and we show that using a radio frequency field allows to selectively address the atoms in these states. This method is used to measure the energy and momentum distribution of the atoms in the localized states. We also discuss possible extensions of this scheme to address and manipulate particles in single lattice sites.

cond-mat.stat-mech↗

arXiv2004

Atom interferometry with trapped Fermi gases

We realize an interferometer with an atomic Fermi gas trapped in an optical lattice under the influence of gravity. The single-particle interference between the eigenstates of the lattice results in macroscopic Bloch oscillations of the sample. The absence of interactions between fermions allows a time-resolved study of many periods of the oscillations, leading to a sensitive determination of the acceleration of gravity. The experiment proves the superiorness of non interacting fermions with respect to bosons for precision interferometry, and offers a way for the measurement of forces with microscopic spatial resolution.

cond-mat.soft↗

arXiv2003

Expansion of a Fermi gas interacting with a Bose-Einstein condensate

We study the expansion of an atomic Fermi gas interacting attractively with a Bose-Einstein condensate. We find that the interspecies interaction affects dramatically both the expansion of the Fermi gas and the spatial distribution of the cloud in trap. We observe indeed a slower evolution of the radial-to-axial aspect ratio which reveals the importance of the mutual attraction between the two samples during the first phase of the expansion. For large atom numbers, we also observe a bimodal momentum distribution of the Fermi gas, which reflects directly the distribution of the mixture in trap. This effect allows us to extract information on the dynamics of the system at the collapse.

cond-mat.soft↗