Fröhlich Mass in GaAs-Based Structures

The Fröhlich interaction is one of the main electron-phonon intrinsic interactions in polar materials originating from the coupling of one itinerant electron with the macroscopic electric field generated by any longitudinal optical (LO) phonon. Infrared magnetoabsorption measurements of doped GaAs quantum well structures have been carried out in order to test the concept of Fröhlich interaction and polaron mass in such systems. These new experimental results lead one to question the validity of this concept in a real system.

Figure 1

Experimental transmission spectra (empty dots) of sample 1200. (a) Absolute transmission for $B=0\mathrm{T}$ and $\theta =60°$. (b),(c) Absolute transmission and relative transmission, respectively, for $B_{\perp }=20.7\mathrm{T}$ and $\theta =20°$. The continuous red curves are the fit of data with the model described in the text.

Figure 2

Observed cyclotron energies for sample 1200 (a) and sample 1211 (b) for different tilt angles. The crosses and black down triangles are the measured LO and TO energies, respectively, and the empty squares the cyclotron energies in the PF configuration. Other points are the observed CR energies in the TF configuration: (a) full dots, $\theta =14°$; empty dots, $\theta =20°$; stars, $\theta =25°$; (b) full dots, $\theta =15°$; empty dots, $\theta =26.5°$. Results in (b) for $B_{\perp }$ lower than 18 T correspond to filling factors $>2$ when nonparabolicity effects are apparent.

Figure 3

Fit of the relative transmission curves for sample 1200 at $\theta =25°$. The curves are shifted for clarity. Empty dots are experimental points and full continuous curves the corresponding calculated relative transmission spectra. The hatched region corresponds to that of $\hslash {\omega }_{\mathrm{TO}}$ (GaAs) (see text).