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HL: Fachverband Halbleiterphysik

HL 5: 2D semiconductors and van der Waals heterostructures I (joint session HL/DS)

HL 5.9: Talk

Monday, September 27, 2021, 16:00–16:15, H4

Microscopic Theory of Exciton-Exciton Annihilation in Two-Dimensional Semiconductors — •Alexander Steinhoff, Matthias Florian, and Frank Jahnke — Institute for Theoretical Physics, University of Bremen, Bremen, Germany

Auger-like exciton-exciton annihilation (EEA) is considered the key fundamental limitation to quantum yield in devices based on excitons in two-dimensional (2d) materials. Since it is challenging to experimentally disentangle EEA from competing processes, guidance of a quantitative theory is highly desirable. The very nature of EEA requires a material-realistic description that is not available to date.

We present a many-body theory of EEA based on first-principle band structures and Coulomb interaction matrix elements that goes beyond an effective bosonic picture. Applying our theory to monolayer MoS₂ encapsulated in hexagonal BN, we obtain an EEA coefficient in the order of 10⁻³ cm²s⁻¹ at room temperature, suggesting that carrier losses are often dominated by other processes, such as defect-assisted scattering.

Our studies open a perspective to quantify the efficiency of intrinsic EEA processes in various 2d materials in the focus of modern materials research.