Interference-induced phenomena in high-order harmonic generation from bulk solids

TL;DR

This study models high-order harmonic generation in bulk solids, revealing how interference among emitted fields from initial states influences harmonic spectra, including suppression of even harmonics and cutoff determination.

Contribution

It introduces a quantum mechanical model that explains interference effects in harmonic generation from bulk solids, emphasizing the role of initial state interference.

Findings

Interference among emitted fields suppresses even harmonics.

The harmonic cutoff is determined by electromagnetic field interference.

The model decouples dynamics of initial Bloch states in the velocity gauge.

Abstract

We consider a quantum mechanical model for the high-order harmonic generation in bulk solids. The bandgap is assumed to be considerably larger than the exciting photon energy. Using dipole approximation, the dynamical equations for different initial Bloch states are decoupled in the velocity gauge. Although there is no quantum mechanical interference between the time evolution of different initial states, the complete harmonic radiation results from the interference of fields emitted by all the initial (valence band) states. In particular, this interference is shown to be responsible for the suppression of the even order harmonics. The number of the observable harmonics (essentially the cutoff) is also determined by electromagnetic field interference.