Hannover 2013 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 40: Quantum gases: Optical lattices II

Q 40.3: Talk

Wednesday, March 20, 2013, 14:30–14:45, A 310

Coherent coupling of Bloch bands in an optical lattice — •Christoph Sträter and Andre Eckardt — Max-Planck-Instuitut für Physik komplexer Systeme, 01387 Dresden, Germany

Ultracold quantum gases in optical lattices potentials have gained a lot of attention as a versatile tool for engineering many-body lattice physics under extremely clean and tunable conditions. In the interesting tight-binding regime of deep lattices, where a description in terms of Hubbard-type models applies, the lowest Bloch band is energetically well separated from excited bands. Therefore, orbital degrees of freedom belonging to excited bands are usually frozen out. Methods that have been used experimentally to include orbital freedom are a π-pulse like population transfer to the excited band via Raman coupling [1] and the rapid ramping of superlattice structures [2], both approaches involve considerable heating. Another scheme consists in using the sublattice orbital degree of freedom of special lattice geometries [3]. We are proposing a different method, namely to coherently couple energetically distant bands by employing an external time-periodic force. Such an approach allows to open the orbital freedom adiabatically in different ways under highly tunable conditions. We derive effective time-independent Hubbard models describing the band-coupled system. Within this framework we study the melting of a bosonic Mott-isulator as a result of the coherent band coupling.

[1] T. Müller, S. Fölling, A. Widera, and I. Bloch, PRL 99, 200405 (2007) [2] G. Wirth, M. Ölschläger, and A. Hemmerich, Nature Phys. 7, 147 (2011) [3] P. Soltan-Panahi et al., Nature Phys. 8, 71 (2012)