GRK 2905 – Ultrafast Nanoscopy
From single particle dynamics to cooperative processes
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GRK Seminar:
doc. RNDr. Tomás Novotný:
January 23 @ 15:00 – 16:00
Optically induced excitonic shifts in transition metal dichalcogenide monolayers
Increasing the speed limits of conventional electronics requires innovative approaches to manipulate other quantum properties of electrons besides their charge or spin. An alternative approach is the manipulation of the valley degree of freedom in semiconductors. In our study, we demonstrate the possibility of the manipulation of such degrees of freedom in transition metal dichalcogenide monolayers using optical pulses on timescales of a few tens of femtoseconds.
We report on the theoretical and experimental investigation of valley-selective optical Stark and Bloch-Siegert shifts of exciton resonances in WSe2 and MoS2 monolayers induced by strong circularly polarized nonresonant optical fields. We predict and observe transient shifts of both 1sA and 1sB exciton transitions in the linear interaction regime. The theoretical description is based on semiconductor Bloch equations. The solutions of the equations are obtained with a modified perturbation technique, which takes into account many-body Coulomb interaction effects. These solutions allow us to explain the polarization dependence of the shifts and calculate their values analytically. We found experimentally the limits of the applicability of the theoretical description by observing the transient exciton spectra change at high field amplitudes of the driving wave.
References:
[1] A. O. Slobodeniuk, P. Koutenský, M. Bartoš, F. Trojánek, P. Malý, T. Novotný, and M. Kozák, npj 2D Mater Appl 7, 17 (2023).
[2] A. O. Slobodeniuk, P. Koutenský, M. Bartoš, F. Trojánek, P. Malý, T. Novotný, and M. Kozák, Phys. Rev. B 106, 235304 (2022).
Venue: RUN auditorium
GRK 2905 & SFB 1277
Host: Ferdiand Evers