Regensburg 2016 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 71: 2D Materials beyond Graphene -Dynamics and Excitation
(Joint session of DS, DY, HL, MA, O and TT organized by O)

TT 71.3: Talk

Thursday, March 10, 2016, 11:15–11:30, S054

Electron dynamics in eiptaxial single layer MoS₂ — •Antonija Grubisic-Cabo¹, Jill A. Miwa¹, Signe S. Gronborg¹, Jonathon M. Riley², Jens C. Johannsen³, Cephise Cacho⁴, Oliver Alexander⁴, Richard T. Chapman⁴, Emma Springate⁴, Marco Grioni³, Jeppe V. Lauritsen¹, Phil D. C. King², Philip Hofmann¹, and Soren Ulstrup¹ — ¹Aarhus University, DK — ²University of St. Andrews, UK — ³Ecole Polytechnique Federale de Lausanne, CH — ⁴CLF, STFC Rutherford Appleton Laboratory, UK

The current understanding of the optical properties and excited carrier dynamics in single-layer and few-layer transition metal dichalcogenides relies largely on a series of photoluminescence and differential absorption measurements. Since excitons dominate the optical response, the dynamics of free carriers cannot be studied directly. Here, we use time- and angle-resolved photoemission spectroscopy to directly measure free carriers in epitaxial single layer MoS₂ grown on either Au(111) or on graphene. For MoS₂/Au(111) we determine an ultrafast (50 fs) extraction of excited free carriers via the metal and ascertain a direct quasiparticle band gap of 1.95 eV. The observed quasiparticle gap is significantly smaller than the theoretically estimated value for free-standing MoS₂. This can be explained by a strong renormalisation of the band gap. For MoS₂ on graphene, we find indications of induced band shifts that lead to a time-dependence of the electronic structure.