



01431nas a2200169   4500008004100000245007100041210006900112260001400181490000700195520091200202100002001114700001801134700001901152700002301171700002301194856004401217       2005                        eng d00aBragg Spectroscopy of ultracold atoms loaded in an optical lattice0 aBragg Spectroscopy of ultracold atoms loaded in an optical latti  c2005/8/120 v723 a  We study Bragg spectroscopy of ultra-cold atoms in one-dimensional optical
lattices as a method for probing the excitation spectrum in the Mott insulator
phase, in particular the one particle-hole excitation band. Within the
framework of perturbation theory we obtain an analytical expression for the
dynamic structure factor $S(q,\omega)$ and use it to calculate the imparted
energy which has shown to be a relevant observable in recent experiments. We
test the accuracy of our approximations by comparing them with numerically
exact solutions of the Bose-Hubbard model in restricted cases and establish the
limits of validity of our linear response analysis. Finally we show that when
the system is deep in the Mott insulator regime, its response to the Bragg
perturbation is temperature dependent. We suggest that this dependence might be
used as a tool to probe temperatures of order of the Mott gap.
1 aRey, Ana, Maria1 aBlakie, Blair1 aPupillo, Guido1 aWilliams, Carl, J.1 aClark, Charles, W.  uhttp://arxiv.org/abs/cond-mat/0406552v2