Quasiparticle dynamics in a Bose insulator probed by inter-band Bragg   spectroscopy
  We investigate experimentally and theoretically the dynamical properties of a Mott insulator in decoupled one-dimensional chains. Using a theoretical analysis of the Bragg excitation scheme we show that the spectrum of inter-band transitions holds information on the single-particle Green's function of the insulator. In particular the existence of particle-hole coherence due to quantum fluctuations in the Mott state is clearly seen in the Bragg spectra and quantified. Finally we propose a scheme to directly measure the full, momentum resolved spectral function as obtained in angle-resolved photoemission spectroscopy of solids. 
Nicole Fabbri, Sebastian D. Huber, David Cl\'ement, Leonardo Fallani,   Chiara Fort, Massimo Inguscio, Ehud Altman
cond-mat.quant-gas quant-ph