Dresden 2017 – scientific programme

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O: Fachverband Oberflächenphysik

O 94: Graphene: Electronic Properties, Structure and Substrate Interaction II

O 94.11: Talk

Thursday, March 23, 2017, 17:30–17:45, TRE Ma

tracking electron dynamics in graphene and TMDCs — •Cephise Cacho — Artemis - Central Laser Facility, Didcot, UK

Novel quantum materials such as graphene and transition metal dichalcogenides (TMDC) are attracting vast interest particularly for their application in spintronic and optoelectronic devices. Their properties are intrinsically governed by the large momentum electrons (at the Brillouin zone K-point). In order to eject such electrons in vacuum and observe their dynamics, a high energy (>20 eV) photon source is required as well as ultrashort pulse duration. High Harmonic Generation source [1] combined to an Angle-Resolved PhotoEmission Spectroscopy (ARPES) end-station is a powerful tool to observe such electron dynamics. After an introduction on ARPES and experimental concepts, I will present an overview of recent time-resolved ARPES studies [2-6] performed at the Artemis facility.

Single-layers of MoS2, WS2 and bulk WSe2 were resonantly pumped across the band gap at the K point. Monitoring the valence/conduction bands population reveals the band dynamics during excitation. Furthermore the intervalley scattering is explored by exciting the surface with circularly polarized light.

References 1. F. Frassetto et al., Optics Express 19, 19169 (2011) 2. E. Pomarico et al., arXiv:1607.02314 (2016) 3. A. Grubišić Čabo et al., Nano Lett. 15, 5883 (2015) 4. S. Ulstrup et al., ACS Nano 10, 6315 (2016) 5. S. Ulstrup et al., arXiv:1608.06023 (2016) 6. R. Bertoni et al., arXiv:1606.03218 (2016)