Role of excitons in double Raman resonances in GaAs quantum wells

Abstract

Raman scattering by longitudinal-optical phonons has been measured in GaAs-AlAs multiple quantum wells at high magnetic fields. Doubly resonant scattering processes are observed at photon energies corresponding to magneto-excitons with different principal quantum numbers for the incoming and outgoing channels. The existence of these initially forbidden scattering processes, their resonance energies, and their relative intensities are correctly reproduced by our theoretical description. The model takes into account the excitonic nature of the intermediate states, as well as scattering processes involving a nonzero in-plane phonon wave vector, which is required to allow inter-Landau level scattering of the exciton.

Emission Excitation Spectroscopy in WS2 Monolayer Encapsulated in Hexagonal BN

“…To verify type of the Raman scattering resonance, i.e., incoming or outgoing [15], the intensity profile for the A 1 (Γ ) mode was determined by fitting of Gaussian function to the emitted signal as a function of tuned laser energy, shown in Fig. 1.…”

Raman Spectroscopy

“…Changes in surface structure after UV laser ablation were observed with a micro-Raman probe (268). Quantum wells in GaAs surfaces have been examined in relation to longitudinal-optical phonons, standing acoustic waves, and Raman efficiency in a planar microcavity (269)(270)(271). Photoluminescence studies were carried out at the interface of GaN and wurtzite layers (272).…”

Exciton-phonon interaction in fractional dimensional space

“…22,23 Thus the dependence of the Fröhlich exciton-optical phonon matrix element on q is important in resonant Raman scattering studies. 24 The interaction of a longitudinal-optical phonon with an excitonic state becomes highly enhanced, when an incident photon becomes resonant with the initial, 1s state. As shown in Figs.…”