Institute of High Pressure Physics

Dear Ladies and Gentlemen,

We are pleased to invite you to the IHPP PAS Seminar on Nitride Semiconductors. The next presentation will be held in a hybrid mode – at the New Technologies seminar room, Al. Prymasa Tysiąclecia 98, and through Zoom platform (to get the link, please contact us at nitride_seminar@mail.unipress.waw.pl ).

The next seminar is scheduled on Monday 22.05.2023 at 14:00.

Speaker: prof. dr hab. Piotr Kossacki (University of Warsaw, Institute of Experimental Physics)

Title: Ultrafast dynamics of excitons in monolayers of semiconductor TMDs

Abstract:
Monolayers of transition metal dichalcogenides (TMDs) draw a lot of attention as semiconducting materials with robust optical properties, strong Coulomb interaction and an optically accessible valley degree of freedom. Extraordinary properties of exciton complexes lead to new possibilities of exploration of nonlinear effects.
In my seminar, I will focus on ultrafast studies of exciton dynamics explored by time resolved photoluminescence, FWM and femtosecond pump-probe experiments. The studies of neutral and charged exciton optical response show strong interactions between different complexes. For example creation of CX population in a given K,K’ valley leads to the capture of available free carriers in the opposite valley and reduces the interaction of neutral X with the Fermi sea. From the valley-resolved analysis of the observed effects we are also able to extract the spin-valley relaxation times of free carriers as a function of carrier density. The several effects related to interaction with carries such as the oscillator strength variation and energy shift will be discussed and compared to the cases of ordinary quantum wells. I will point similarities and differences in the complex landscape of exciton-exciton and exciton-carrier interactions in both two dimensional systems.

Sincerely,

Tadeusz Suski
Piotr Perlin
Anna Kafar