University of Birmingham > Talks@bham > Cold Atoms > Dynamics of ultracold Fermions in optical lattices

Dynamics of ultracold Fermions in optical lattices

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  • UserChristoph Becker (Hamburg)
  • ClockWednesday 09 May 2012, 11:00-12:00
  • HousePhysics East 217.

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Quantum gases in optical lattices offer a wide range of applications for quantum simulation due to the full control over lattice and interaction parameters as well as the internal atomic degrees of freedom. In our setup, we produce different interacting spin-mixtures of fermionic potassium atoms and load them into an optical lattice. The atoms behave similar to electrons in a crystal. However, in contrast to electrons with spin-1/2, we use 40K with a higher spin, which has important effects on the properties of the system. The atomic ensemble is quenched from a polarized to a non-polarized regime and the resulting dynamics are recorded. We compare our data to a theoretical calculation. In the latter, we assume a simplified two-particle model which is in very good agreement with our observations. Our results open new perspectives to study magnetism of fermionic lattice systems beyond conventional spin-1/2 systems.

Another intruiging property of electrons in solid state systems is their dynamical response to an external perturbation, e.g. charge transport in electric fields. It is highly interesting to investigate the dynamical properties of ultracold fermions in optical lattices and compare these results to charge transport prperties of solid state systems. For this, we prepare spin-polarized fermions in a shallow 1D-lattice, excite a small fraction to the third band using lattice amplitude modulation and thus create particle-hole pairs with a well-defined momentum. We observe the time evolution of the particle-hole pair in momentum space which reveals an oscillatory behavior. The oscillation frequency is dependent on the initial momentum of the excitations, the trapping frequency of the harmonic confinement and the lattice depth. We compare our data to a single-particle quantum model yielding very good quantitative agreement. Our findings will allow us to investigate the dynamical properties of interacting Fermi spin-mixtures as well as transport properties of fermionic quantum gases in higher bands.

This talk is part of the Cold Atoms series.

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