Coherent phenomena in semiconductors

Abstract

A review of coherent phenomena in photoexcited semiconductors is presented. In particular, two classes of phenomena are considered: On the one hand the role played by optically-induced phase coherence in the ultrafast spectroscopy of semiconductors; On the other hand the Coulomb-induced effects on the coherent optical response of low-dimensional structures.All the phenomena discussed in the paper are analyzed in terms of a theoretical framework based on the density-matrix formalism. Due to its generality, this quantumkinetic approach allows a realistic description of coherent as well as incoherent, i.e. phase-breaking, processes, thus providing quantitative information on the coupledcoherent vs. incoherent-carrier dynamics in photoexcited semiconductors.The primary goal of the paper is to discuss the concept of quantum-mechanical phase coherence as well as its relevance and implications on semiconductor physics and technology. In particular, we will discuss the dominant role played by optically induced phase coherence on the process of carrier photogeneration and relaxation in bulk systems. We will then review typical field-induced coherent phenomena in semiconductor superlattices such as Bloch oscillations and Wannier-Stark localization. Finally, we will discuss the dominant role played by Coulomb correlation on the linear and non-linear optical spectra of realistic quantum-wire structures.

Observation of Photon-Assisted Tunneling in Optical Lattices

“…The static force leads to a suppression of resonant tunneling between the ground states. This suppression and the related Wannier-Stark localization of the wavefunction have been intensively discussed in the theoretical literature [9,10]. In this work, we report a direct measurement of this suppression based on the spatial tunneling of the condensate atoms.…”

High-harmonic generation from Bloch electrons in solids

“…The electron dynamics in a solid interacting with an electromagnetic field are generally considered to have a contribution from both intra-band and inter-band dynamical processes [16][17][18], as illustrated in Fig. 1.…”

Ultrafast carrier dynamics in semiconductor nanostructures: interplay between coherence and relaxation

“…Both classes of phenomena typically occur on a pico-or femtosecond timescale, where the coupling between coherent and incoherent carrier dynamics may play a dominant role [5]. Therefore, an adequate theoretical model of the ultrafast dynamics on this timescale must account for both coherent and incoherent effects on the same kinetic level.…”