SKM 2023 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 24: Quantum dots: Optics

HL 24.7: Vortrag

Mittwoch, 29. März 2023, 11:00–11:15, POT 151

Exciton diffusion in a quantum dot ensemble — •Karol Kawa and Paweł Machnikowski — Wrocław University of Science and Technology, 50-370 Wrocław, Poland

We study theoretically Förster transfer [1] of an exciton in an ensemble of quantum dots (QDs) randomly distributed on a circular mesa. In such a system energy transfer was observed experimentally within a spatially resolved photoluminescene sprectroscopy [2]. The analytical form of Förster coupling in the general ensemble of quantum dipole emitters is known [3–5]. It is a sum of three power-law terms diminishing with distance, each multiplied by an oscillating factor. The fundamental transition energy in each QD is randomized. We solve the equation of motion for the density matrix using the stochastic simulation method with a given exciton decay rate. Then, we present the evolution of the exciton mean square displacement (MSD) from the initially excited QD. It runs in three time stages. First, a ballistic motion, followed by a standard diffusion, which ends at saturation. Using an approximate analytical approach [6], we provide formulas that qualitatively reproduce all stages of the MSD.

[1] T. Förster, Ann. Phys., 437, 55 (1948)

[2] F.V. de Sales et al., Phys. Rev. B 70, 235318 (2004)

[3] M.J. Stephen, J. Chem. Phys. 40, 669 (1964)

[4] R.H. Lehmberg, Phys. Rev. A 2, 883 (1970)

[5] F. Miftasani and P. Machnikowski, Phys. Rev. B 93, 075311 (2016)

[6] K. Kawa and P. Machnikowski, Phys. Rev. B 102, 174203 (2020)