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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 Ulstrup11Aarhus 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.

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