Cooper minimum of high-order harmonic spectra from an MgO crystal in an ultrashort laser pulse

Cooper minimum structure of high-order harmonic spectra from atoms or molecules has been extensively studied. In this paper, we demonstrate that the crystal harmonic spectra from an ultrashort midinfrared laser pulse also exhibit the Cooper minimum characteristic. Based on the accurate band dispersion and k-dependent transition dipole moment (TDM) from the first-principles calculations, it can be found that the harmonic spectra from the MgO crystal along the Gamma-X direction present a dip structure in the plateau, which is originated from the valley of TDM by examining the distribution of the harmonic intensity at the k space. The Cooper minimum feature in crystal high-order-harmonic generation (HHG) will pave a new way to retrieve the band information of solid materials by using HHG from the ultrashort midinfrared laser pulse.