  An exotic phase, the bond order wave, characterized by the spontaneous
dimerization of the hopping, has been predicted to exist sandwiched between the
band and Mott insulators in systems described by the ionic Hubbard model.
Despite growing theoretical evidences, this phase still evades experimental
detection. Given the recent realization of the ionic Hubbard model in ultracold
atomic gases, we propose here to detect the bond order wave using superlattice
modulation spectroscopy. We demonstrate, with the help of time-dependent
density-matrix renormalization group and bosonization, that this spectroscopic
approach reveals characteristics of both the Ising and Kosterlitz-Thouless
transitions signaling the presence of the bond order wave phase. This scheme
also provides insights into the excitation spectra of both the band and Mott
insulators.
