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Non-Equilibrium Dynamics in Ultracold Interacting Atoms

Non-Equilibrium Dynamics in Ultracold Interacting Atoms. Sergio Smith (Howard University). Simulations of Ultracold Atoms in Optical Lattices. I ntroduction. Ultracold atoms ( <1 μ K ) Cold enough to be trapped and studied Laser and evaporative cooling Bose-Einstein Condensates (BECs)

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Non-Equilibrium Dynamics in Ultracold Interacting Atoms

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  1. Non-Equilibrium Dynamics in Ultracold Interacting Atoms Sergio Smith (Howard University) Simulations of Ultracold Atoms in Optical Lattices

  2. Introduction • Ultracold atoms ( <1μK ) • Cold enough to be trapped and studied • Laser and evaporative cooling • Bose-Einstein Condensates (BECs) • Magnetic moment • Two-level system: spin up and spin down • Optical lattice • Grid of standing light waves • Potential wells at highest intensity locations

  3. Quantum effects • Quantized energy levels • Lowest energy state • Wave-particle duality • Tunneling E4 E3 E2 E1

  4. The Experiment • Two-dimensional lattice • Atoms loaded into wells • Two sub-lattices • Rubidum-87 atoms • Cool evaporatively • Become BECs • Potential lowered to allow tunneling • Measured quantity: Staggered Magnetization • Distribution of atoms on sub-lattices

  5. Simulation • Wave function • Single site ≈ Gaussian • Random initial phase • Some phase “memory” governed by α. • Many-body system • Sum of local functions • Disregard spatial evolution • Discretized Gross-Pitaevskii Equation

  6. Results J →J+δJ U=0.03J O= Experimental Data α=0.6 α=0.8 • Good qualitative agreement • Calculated value of J was wrong • Possibly due to screening effect

  7. Relevance and Future Research • Optical lattice experiments provide a highly tunable environment to study magnetism in BECs, with relevance to high-temperature superconductors. • Future research includes: • Fine-tuning J and α to fit experimental results • Studying what causes these discrepancies

  8. Acknowledgements • Dr. Michael Foss-Feig • Staff of Joint Quantum Institute (JQI) and Institute for Research in Electronics and Applied Physics (IRAEP) at the University of Maryland, College park.

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