Ursula Keller wins “Swiss Nobel” Marcel Benoist Prize
Farewell: the NCCR MUST ended 
MUST2022 Conference
New scientific highlights
FELs of Europe prize for Jeremy Rouxel
Ruth Signorell wins Doron prize
New FAST-Fellow Uwe Thumm at ETH
International Day of Women and Girls in Science
New scientific highlight
EU XFEL Young Scientist Award for Camila Bacellar,
Prizes for Giulia Mancini and Rebeca Gomez Castillo
Nobel Prize in Chemistry awarded to RESOLV Member Benjamin List
Hans Jakob Wörner invited to give the „New Horizons Solvay Lectures” 
Unusual keynote talk at an international scientific conference
NCCR MUST at Scientifica 2021Tracking electron dynamics in graphene and transition metal dichalcogenide
| Date | Do, 24.11.2016 | |
| Time | 16:30 | |
| Speaker | Dr. Céphise Cacho Artemis Central Laser Facility, Rutherford Appleton Laboratory, United Kingdom | |
| Location | EPFL CH G1 495, Lausanne | |
| Program | Abstract 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 few recent time-resolved ARPES studies performed at the Artemis facility. A quasi-free-standing monolayer of graphene (MLG) is optically excited in a direct interband regime. The measurement of the electronic temperature reveals the role of the supercollisions during the cooling process of the electrons [2]. Over ~100 fs, a population inversion across the Dirac point is observed [3] supporting the potential of graphene for THz amplification applications. Single-layers of MoS2 [4-5], WS2 [6] and bulk WSe2 [7] were resonantly pumped across the band gap at the K point. Measurements of the valence and conduction bands populations give access to the direct quasiparticle band gap [4]. Depending on the screening effects a strong band gap renormalization can be induced [5] by optically excited free charge carriers. Control of spin- and valley-quantum numbers in valence and conduction bands is achieved [6-7] by using circularly polarized optical excitation. 1. F. Frassetto et al., Optics Express 19, 19169 (2011) 2. J. Johannsen et al., Phys Rev Lett 111, 027403 (2013) 3. I. Gierz et al., Nature Materials 12, 1119 (2013) 4. A. Grubišić Čabo et al., Nano Lett. 15, 5883 (2015) 5. S. Ulstrup et al., ACS Nano 10, 6315 (2016) 6. S. Ulstrup et al., arXiv:1608.06023 (2016) 7. R. Bertoni et al., arXiv:1606.03218 (2016) |
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| Link | LACUS | |
