Coherence of Elementary Excitations in a Disordered Electron System

Abstract

The localization properties of the single-particle and collective electron excitations were investigated in the intentionally disordered GaAs/AlGaAs superlattices by weak-field magnetoresistance and Raman scattering. The localization length of the individual electron was found to be considerably larger than that of the collective excitations. This suggests that the disorder has a weaker effect on the electrons than on their collective motion and that the interaction which gives rise to the collective effects increases localization.

Localization in random electron systems:AlxGa1−xAsalloys and intentionally disordered<

“…In the above cited article, 8 we demonstrated that the electron localization length is considerably longer than that of the plasmons, which implies that the electron-electron interaction increases localization. The data were obtained in three samples.…”

“…These measurements were realized in the square shaped-double-mesa structures with areas of 1 ϫ 1 mm 2 described in Ref. 8. Magnetotransport measurements parallel to the layers were realized in the identical SLs grown on semi-insulating substrates.…”

“…8, the electron phase-breaking length determined by the magnetoresistance measurements was used to estimate the localization length of the single-particle electron excitations. In the weak-localization regime ͑k F l ӷ 1, where k F and l are the Fermi wave number and the elastic free path length, respectively͒ and in a weak magnetic field ͑ c Ӷ 1, where c and are the cyclotron frequency and the elastic scattering time, respectively͒, the magnetic field dependence of the conductivity is caused by the weak-localization correction.…”

“…Another method to examine the influence of the interaction on localization of electrons was presented in our recent publication. 8 In this work, we compared the localization lengths of the single-particle and collective electron excitations ͑plasmons͒ in disordered electron systems created by the random potential of intentionally disordered semiconductor superlattices ͑SLs͒. The SLs were grown to produce a Gaussian-type energy disorder, characterized by a controlled strength parameter.…”