Dresden 2017 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 26: Two-Dimensional Materials III (joint session DS, HL, TT, organized by HL)
TT 26.2: Talk
Tuesday, March 21, 2017, 09:45–10:00, POT 51
Band-gap and exciton binding-energy renormalizations due to excited carriers in monolayer TMDs — •Daniel Erben1, Christopher Gies1, Malte Rösner1,2, Alexander Steinhoff1, Matthias Florian1, Michael Lorke1, Tim Wehling1,2, and Frank Jahnke1 — 1Insitute for Theoretical Physics, University of Bremen, Germany — 2Bremen Center for Computational Materials Science, University of Bremen, Germany
Coulomb interaction between charge carriers in atomically thin layers of transition-metal dichalcogenides (TMDs) has been shown to be exceptionally large due to the weak screening in the thin layer itself. It causes strong renormalization effects which change the electronic properties and the optical response of the material.
We investigate excited-state optical properties of the typical monolayer TMDs MoS2, MoSe2, WS2 and WSe2 by solving the semiconductor Bloch equations on the full Brillouin zone using the SXCH-approximation for the Coulomb interaction. Excitonic resonances shift in absolute value and relative to each other with increasing carrier density. This effect is a result of a band-gap reduction due to many-particle renormalizations and a reduction of the binding energy due to screening of the Coulomb interaction and Pauli blocking, which we analyse and compare in detail for MoS2, MoSe2, WS2 and WSe2. Our calculations predict a transition from a direct to an indirect band-gap in molybdenum and tungsten disulfides in the presence of highly excited carriers. The selenides stay indirect for different excitations.