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Title: Artur Slobodeniuk: Dark excitons in monolayers of transition metal dichalcogenides: prediction, probing and manipulation
Number: 63/21
Status: Closing date exceeded
Begin: Thursday, 25.11. 2021, 13:00
Tutor: Karel Carva
Location: Lecture room F2, MFF UK (first floor, Ke Karlovu 5, Praha 2) , and via the zoom meeting https://cesnet.zoom.us/j/99050057205

Thursday 25 November 2021 at 14:00

Lecture room - F2 (MFF, UK, Ke Karlovu 5, first floor), and via the zoom meeting
https://cesnet.zoom.us/j/99050057205
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Dr. Artur Slobodeniuk

DCMP, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, 121 16 Praha 2

Dark excitons in monolayers of transition metal dichalcogenides: prediction, probing and manipulation

Monolayers of semiconducting transition metal dichalcogenides are two-dimensional direct-gap systems that host tightly-bound excitons with an internal degree of freedom corresponding to the valley of the constituting carriers. Strong spin-orbit interaction and the resulting ordering of the spin-split subbands in the valence and conduction bands make the lowest-lying excitons in WX2 (X being S or Se) spin-forbidden and optically dark. We theoretically demonstrate the existence of two types of dark excitons – “Grey” and “Dark”, which appear due to the intrinsic exchange interaction in the monolayer. We describe the properties of these excitons and propose the mechanisms of their optical activation. With polarization-resolved photoluminescence experiments performed on a WSe2 monolayer encapsulated in a hexagonal boron nitride, we show how the intrinsic exchange interaction in combination with the applied in-plane and/or out-of-plane magnetic fields enables one to probe and manipulate the valley degree of freedom of the dark excitons.