Optical Orientation of Excitons in a Longitudinal Magnetic Field in Indirect-Band-Gap (In,Al)As/AlAs Quantum Dots with Type-I Band Alignment

• Published in: Nanomaterials (Basel, Switzerland) Vol. 13; no. 4; p. 729
• Main Authors: Shamirzaev, T. S., Shumilin, A. V., Smirnov, D. S., Kudlacik, D., Nekrasov, S. V., Kusrayev, Yu G., Yakovlev, D. R., Bayer, M.
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 14.02.2023; MDPI
• Subjects: Alignment; Aluminum arsenides; Band theory (Physics); Circular polarization; Electron spin; Energy gap; Exciton theory; Excitons; hyperfine interaction; Lasers; Magnetic fields; Magnetic properties; Materials research; Nuclear spin; optical orientation; Optical properties; Optics; Population dynamics; Quantum dots; Recombination; spin blockade; Spin dynamics; spins; Russia; spins; quantum dots; excitons; optical orientation; hyperfine interaction; spin blockade
• ISSN: 2079-4991; 2079-4991
• DOI: 10.3390/nano13040729

Exciton recombination and spin dynamics in (In,Al)As/AlAs quantum dots (QDs) with indirect band gap and type-I band alignment were studied. The negligible (less than 0.2 μeV) value of the anisotropic exchange interaction in these QDs prevents the mixing of the excitonic basis states and makes the formation of spin-polarized bright excitons possible under quasi-resonant, circularly polarized excitation. The recombination and spin dynamics of excitons are controlled by the hyperfine interaction between the electron and nuclear spins. A QD blockade by dark excitons was observed in the magnetic field, that eliminates the impact of nuclear spin fluctuations. A kinetic model which accounts for the population dynamics of the bright and dark exciton states as well as for the spin dynamics was developed to quantitatively describe the experimental data.