Multi-band spectroscopy of ultracold fermions: Observation of reduced   tunneling in attractive Bose-Fermi mixtures
  We perform a detailed experimental study of the band excitations and tunneling properties of ultracold fermions in optical lattices. Employing a novel multi-band spectroscopy for fermionic atoms we can measure the full band structure and tunneling energy with high accuracy. In an attractive Bose-Fermi mixture we observe a significant reduction of the fermionic tunneling energy, which depends on the relative atom numbers. We attribute this to an interaction-induced increase of the lattice depth due to self-trapping of the atoms. 
J. Heinze, S. G\"otze, J. S. Krauser, B. Hundt, N. Fl\"aschner, D.-S.   L\"uhmann, C. Becker, and K. Sengstock
cond-mat.quant-gas