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Laser Physics

Effects of static and random magnetic fields on atoms in a gray optical lattice

Natalya V. Morrow, S. K. Dutta, Georg A. Raithel

Published Jul 1, 2007• 0 citations
Publisher

Abstract

We study magnetic field-induced modifications of the well-to-well tunneling behavior of atoms in a one-dimensional grey optical lattice. Measurements of the tunneling frequency as a function of the applied magnetic field reveal several tunneling resonances. We further show that the tunneling signal can be suppressed by randomly varying the symmetry of the potential wells. The tunneling is suppressed most effectively if the autocorrelation time of the lattice-well variation is on the order of the tunneling time. Experimental and theoretical results are in good agreement.

DOI
10.1134/s1054660x07070080

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We study magnetic field-induced modifications of the well-to-well tunneling behavior of atoms in a one-dimensional grey optical lattice. Measurements of the tunneling frequency as a function of the applied magnetic field reveal several tunneling resonances. We further show that the tunneling signal can be suppressed by randomly varying the symmetry of the potential wells. The tunneling is suppressed most effectively if the autocorrelation time of the lattice-well variation is on the order of the tunneling time. Experimental and theoretical results are in good agreement.
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We present a theoretical investigation of the temperature and of the magnetization of atoms in one-dimensional ``gray'' optical lattices. Such lattices consist of counterpropagating beams having crossed linear polarizations, tuned on the blue side of a J\ensuremath{\rightarrow}J or a J\ensuremath{\rightarrow}J-1 transition, and a static longitudinal magnetic field. The variation of the atomic temperature with the magnetic field recently observed (an increase at low magnetic field; a decrease towards an asymptotic value at high magnetic field) is found for any atomic transition admitting one or two uncoupled states. This change of behavior of the temperature results from a qualitative change of the cooling mechanism and is correlated with a transition from paramagnetism to antiparamagnetism in the optical lattice. \textcopyright{} 1996 The American Physical Society.
We report experimental results on the properties of Bose-Einstein condensates in one-dimensional optical lattices. By accelerating the lattice, we observed Bloch oscillations of the condensate in the lowest band, as well as Landau-Zener (LZ) tunneling into higher bands when the lattice depth was reduced and/or the acceleration of the lattice was increased. The dependence of the LZ 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 time-orbiting-potential trap on our experimental results.
We use Raman-assisted tunneling in an optical superlattice to generate large tunable effective magnetic fields for ultracold atoms. When hopping in the lattice, the accumulated phase shift by an atom is equivalent to the Aharonov-Bohm phase of a charged particle exposed to a staggered magnetic field of large magnitude, on the order of one flux quantum per plaquette. We study the ground state of this system and observe that the frustration induced by the magnetic field can lead to a degenerate ground state for non-interacting particles. We provide a measurement of the local phase acquired from Raman-induced tunneling, demonstrating time-reversal symmetry breaking of the underlying Hamiltonian. Furthermore, the quantum cyclotron orbit of single atoms in the lattice exposed to the magnetic field is directly revealed.