Elementary excitations in charge-tunable InGaAs quantum dots studied by resonant Raman and resonant photoluminescence spectroscopy

TL;DR

This study uses resonant optical spectroscopy to investigate charge-tunable InGaAs quantum dots, revealing how electron number influences elementary excitations, many-particle interactions, and polaronic effects.

Contribution

It provides detailed spectroscopic analysis of how electron occupancy affects excitations and interactions in quantum dots, highlighting differences between N=1 and N=2 electron states.

Findings

Distinct Raman spectra for N=1 and N=2 electrons

Observation of singlet and triplet transitions at N=2

Polaronic effects are strong at N=1 and suppressed at N=2

Abstract

We report on resonant optical spectroscopy of self-assembled InGaAs quantum dots in which the number of electrons can accurately be tuned to N=0,1,2 by an external gate voltage. Polarization, wave vector and magnetic field dependent measurements enable us to clearly distinguish between resonant Raman and resonant photoluminescence processes. The Raman spectra for N=1 and 2 electrons considerably differ from each other. In particular, for N=2, the quantum-dot He, the spectra exhibit both singlet and triplet transitions reflecting the elementary many-particle interaction. Also the resonant photoluminescence spectra are significantly changing by varying the number of electrons in the QDs. For N=1 we observe strong polaronic effects which are suppressed for N=2.