Dresden 2017 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 5: Focus Session: Two-dimensional materials I (joined session with TT)

HL 5.6: Hauptvortrag

Montag, 20. März 2017, 11:30–12:00, POT 81

Excitons in ultra-thin perovskites & van der Waals crystals — •Alexey Chernikov — Department of Physics, University of Regensburg, Germany

Excitons, as first introduced by J. Frenkel in 1931, are fundamental quasiparticles in semiconductors, composed from an excited electron and the remaining hole with an effective positive charge bound together by the Coulomb interaction. The excitons strongly influence the materials` response to external fields and perturbations, and are of particular importance for a variety of applications, including solar cells, light emitters, lasers, modulators, and detectors. In addition, they play a major role in more advanced concepts, such as entangled photons from biexciton sources, excitonic qubits, carrier multiplication, and Bose-Einstein condensation.

In this talk, I will focus on the properties of excitonic particles in nanostructured two-dimensional materials: single layers of semiconducting organic-inorganic perovskites and van der Waals crystals as thin as a single unit cell. I will discuss the nature of an unusually strong and unconventional Coulomb interaction shared by these systems and demonstrate how it results in exciton binding energies as large as 0.5 eV with highly efficient light-matter interaction, largely determining the optical response of these ultra-thin layers. Finally, I will outline how the excitons can be externally tuned either by electrical and optical injection of charge carriers or through the dielectric engineering of the environment in heterostructures.