|
Seminal experiments on ultracold gases of atoms trapped in optical
lattices [1,2,3] have lately turned the spotlight of scientific research
interest on the Bose-Hubbard model and its variants.
In our recent work [4], we investigated spectral excitations of the disordered Bose-Hubbard model by means of the variational cluster approach. We consider two common experimental methods used to induce disorder leading to qualitatively different disorder distributions: (i) superposition of two laser fields with incommensurate wavevectors and (ii) the addition of a laser speckle field to the main optical lattice. The computed spectra exhibit a strong dependence on the shape of the disorder distribution and the disorder strength. In addition, we compare alternative results for the Mott gap obtained from its formal definition and from the minimum peak distance, which is the quantity available from experiments. Our results provide crucial information for Bragg spectroscopy experiments with ultracold atoms trapped in optical lattices, where it became only recently possible to measure wave vector resolved spectral excitations. Thus, our numerical results might proof useful for interpreting the experimental data. [1] D. Jaksch, C. Bruder, J. I. Cirac, C. W. Gardiner, and P. Zoller, Phys. Rev. Lett. 81, 3108 (1998). [2] M. Greiner, O. Mandel, T. Esslinger, T. W. Hansch, and I. Bloch, Nature 415, 39 (2002). [3] I. Bloch, J. Dalibard, and W. Zwerger, Rev. Mod. Phys. 80, 885 (2008). [4] M. Knap, E. Arrigoni, and W. von der Linden, arXiv:1007.2716 (2010). |
|