Dresden 2006 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 16: Solids At Low Temperature: Quantum Liquids, Bose-Einstein Condensates, Ultra-cold Atoms, ...

TT 16.4: Vortrag

Dienstag, 28. März 2006, 10:15–10:30, HSZ 105

Temperature in One-Dimensional Bosonic Mott Insulators — •Kai P. Schmidt¹, Alexander Reischl², and Götz S. Uhrig³ — ¹Institute of Theoretical Physics, École Polytechnique Fédérale de Lausanne, CH 1015 Lausanne, Switzerland — ²Institut für Theoretische Physik, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany — ³Theoretische Physik, Geb. 38, FR 7.1, Universität des Saarlandes, D-66123 Saarbrücken, Germany

The Mott insulating phase of a one-dimensional bosonic gas trapped in optical lattices is described by a Bose-Hubbard model. A continuous unitary transformation is used to map this model onto an effective model conserving the number of elementary excitations. We obtain quantitative results for the kinetics and for the spectral properties of the low-energy excitations for a broad range of parameters in the insulating phase. By these results, recent Bragg spectroscopy experiments are explained. Evidence for a significant temperature of the order of the microscopic energy scales is found. The temperature scale deduced from the spectroscopy is embedded in a consistent picture of the thermodynamic properties of bosons in the Mott insulating phase when loaded adiabatically into one-dimensional optical lattices. We find a crucial dependence of the temperature in the optical lattice on the doping level of the Mott insulator. In the undoped case, the temperature is of the order of the large onsite Hubbard interaction. In contrast, at a finite doping level the temperature jumps almost immediately to the order of the small hopping parameter.