Bloch Oscillation under a Bichromatic Laser: Quasi-Miniband Formation, Collapse, and Dynamical Delocalization and Localization

TL;DR

This paper investigates how bichromatic laser driving influences Bloch oscillations in semiconductor superlattices, leading to quasi-miniband formation, collapse, and electron localization or delocalization through multi-photon processes.

Contribution

It introduces a new laser configuration to control electron dynamics in superlattices, revealing mechanisms for dynamical delocalization and localization via multi-photon interactions.

Findings

Quasi-minibands form and collapse under bichromatic laser driving.

Multi-photon processes induce electron localization and delocalization.

The laser frequency difference matches the Wannier-Stark ladder spacing.

Abstract

A novel DC and AC driving configuration is proposed for semiconductor superlattices, in which the THz AC driving is provided by an intense bichromatic cw laser. The two components of the laser, usually in the visible light range, are near but not exactly resonant with interband Wannier-Stark transitions, and their frequency difference equals the Wannier-Stark ladder spacing. Multi-photon processes with the intermediate states in the conduction (valence) band cause dynamical delocalization and localization of valence (conduction) electrons, and the corresponding formation and collapse of the quasi-minibands.