Many-body Effects on Excitonic Optical Properties of Photoexcited Semiconductor Quantum Wire Structures

Abstract

We study carrier interaction induced many-body effects on the excitonic optical properties of highly photoexcited one-dimensional semiconductor quantum wire systems by solving the dynamically screened Bethe-Salpeter equation using realistic Coulomb interaction between carriers. Including dynamical screening effects in the electron/hole self-energy and in the electron-hole interaction vertex function, we find that the excitonic absorption is essentially peaked at a constant energy for a large range of photoexcitation density ($n= 0-6\times 10^5$ cm$^{-1}$), above which the absorption peak disappears without appreciable gain i.e., \textit{no} exciton to free electron-hole plasma Mott transition is observed, in contrast to previous theoretical results but in agreement with recent experimental findings. This absence of gain (or the non-existence of a Mott transition) arises from the strong inelastic scattering by one-dimensional plasmons or charge density excitations, closely related to the non-Fermi liquid nature of one-dimensional systems. Our theoretical work demonstrates a transition or a crossover in one-dimensional photoexcited electron-hole system from an effective Fermi liquid behavior associated with a dilute gas of noninteracting excitons in the low density region ($n<10^5$ cm$^{-1}$) to a non-Fermi liquid in the high density region ($n>10^5$ cm$^{-1}$). The conventional quasi-static approximation for this problem is also carried out to compare with the full dynamical results. Numerical results for exciton binding energy and absorption spectra are given as functions of carrier density and temperature.