Intersublevel Polaron Dephasing in Self-Assembled Quantum Dots

TL;DR

This study investigates polaron dephasing in InAs/GaAs quantum dots using FWM spectroscopy, revealing coherent phonon oscillations and long dephasing times, with temperature effects explained by phonon interactions.

Contribution

It provides the first detailed analysis of polaron dephasing dynamics in self-assembled quantum dots, highlighting the role of acoustic phonons and demonstrating agreement between experiment and theory.

Findings

Oscillatory FWM signals due to coherent phonons

Long dephasing times of 90 ps in quantum dots

Temperature dependence explained by phonon processes

Abstract

Polaron dephasing processes are investigated in InAs/GaAs dots using far-infrared transient four wave mixing (FWM) spectroscopy. We observe an oscillatory behaviour in the FWM signal shortly (< 5 ps) after resonant excitation of the lowest energy conduction band transition due to coherent acoustic phonon generation. The subsequent single exponential decay yields long intraband dephasing times of 90 ps. We find excellent agreement between our measured and calculated FWM dynamics, and show that both real and virtual acoustic phonon processes are necessary to explain the temperature dependence of the polarization decay.