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

TL;DR

This paper demonstrates that high-order harmonic spectra from MgO crystals under ultrashort laser pulses exhibit a Cooper minimum, revealing new insights into solid-state band structures through HHG spectroscopy.

Contribution

It shows for the first time that crystal harmonic spectra can display Cooper minima, linking HHG features to band structure information in solids.

Findings

Harmonic spectra from MgO show a dip structure in the plateau.

The dip originates from the valley of the transition dipole moment.

This reveals a new method to probe band structures using HHG.

Abstract

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 mid-infrared laser pulse also exhibit the Cooper minimum characteristic. Based on the accurate band dispersion and k-dependent transition dipole moment (TDM) from the first-principle calculations, it can be found that the harmonic spectra from MgO crystal along {\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 HHG will pave a new way to retrieve the band information of solid materials by using HHG from the ultrashort mid-infrared laser pulse.