Abstract
We consider the motion of charge carriers in a bulk wide-gap dielectric interacting with a few-cycle laser pulse. A semiclassical model based on Bloch equations is applied to describe the emerging time-dependent macroscopic currents for laser intensities close to the damage threshold. At such laser intensities, electrons can reach edges of the first Brillouin zone even for electron–phonon scattering rates as high as those known for SiO2. We find that, whenever this happens, Bragg-like reflections of electron waves, also known as Bloch oscillations, affect the dependence of the charge displaced by the laser pulse on its carrier–envelope phase.
Highlights
The motion of conduction-band electrons in a crystalline solid is usually considered to be similar to that in free space, apart from scattering processes
Electrons can reach edges of the first Brillouin zone even for electron–phonon scattering rates as high as those known for SiO2. Whenever this happens, Bragg-like reflections of electron waves, known as Bloch oscillations, affect the dependence of the charge displaced by the laser pulse on its carrier–envelope phase
While the kinetic energy of a free electron exposed to a constant external field would indefinitely increase, an electron in a crystal first slows down until it reaches the top of the energy band, and it moves in the opposite direction towards the bottom of the band
Summary
The motion of conduction-band electrons in a crystalline solid is usually considered to be similar to that in free space, apart from scattering processes. The situation is radically different in the case where an external electric field is so strong that, in spite of scattering, an electron can acquire such a high crystal momentum that it reaches an edge of the first Brillouin zone. In the semiclassical picture neglecting scattering, the electron would move periodically back and forth between its initial and final positions. This phenomenon is known as Bloch oscillations[1], and it leads to Wannier–Stark localization[2]. We use the term ’dynamical Bloch oscillations’ to describe phenomena that occur whenever an electron wave is reflected at an edge of the Brillouin zone
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