Terahertz dephasing of intersublevel transitions in InAs/GaAs quantum dots
Terahertz dephasing of intersublevel transitions in InAs/GaAs quantum dots
Schneider, H.; Teich, M.; Winnerl, S.; Stephan, D. R.; Wilson, L. R.; Helm, M.
Semiconductor quantum dots (QD) exhibit a discrete spectrum of bound electronic sublevels. While interband transitions in these synthetic quasi-atoms have been exploited intensively, much less attention has been devoted to excitation between sublevels within the same band. Only recently a systematic study of electron intersublevel relaxation has been reported at various energies below the longitudinal optical phonons [1]. In particular, very long electronic relaxation times up to >1 ns were observed. Therefore the question arises whether the associated dephasing time T2 has similar values.
We will report on THz four-wave mixing (FWM) in self-assembled InAs/GaAs QDs using the free-electron laser FELBE at HZDR. In these QDs, the s-p intersublevel transition has been reduced by interdiffusion to energies below the Reststrahlen band. Dephasing times up to 600 ps have been determined at 18 meV photon energy. By comparing pump-probe and four-wave mixing measurements, we find that dephasing is mainly caused by acoustic phonon scattering, and that there is no significant influence of any pure dephasing process at low temperature [2]. The latter property makes QDs promising for quantum optical applications at THz frequencies.
[1] E. A. Zibik et al., Nature Materials 8, 803 (2009).
[2] M. Teich et al., , Appl. Phy. Lett. 103, 252110 (2013).
Keywords: terahertz; intersublevel transitions; quantum dot; carrier relaxation
Involved research facilities
- Radiation Source ELBE DOI: 10.17815/jlsrf-2-58
Related publications
- DOI: 10.17815/jlsrf-2-58 is cited by this (Id 21443) publication
-
Lecture (Conference)
Fifth International Symposium on Terahertz Nanoscience (TeraNano V), 01.-05.12.2014, Fort-de-France, Frankreich
Permalink: https://www.hzdr.de/publications/Publ-21443