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SUMMARY:Tracking electron dynamics in graphene and transition metal dichal
 cogenide
DTSTART:20161124T163000
DTEND:20161124T173000
DTSTAMP:20260408T012923Z
UID:d21278bb5c65712f2af18350078cd0a89fee9519b1536d011b62a7dd
CATEGORIES:Conferences - Seminars
DESCRIPTION:Dr. Céphise Cacho\nArtemis Central Laser Facility I Rutherfo
 rd Appleton Laboratory\nUnited Kingdom\nNovel quantum materials such as g
 raphene and transition metal dichalcogenides (TMDC) are attracting vast i
 nterest particularly for their application in spintronic and optoelectroni
 c devices. Their properties are intrinsically governed by the large momen
 tum electrons (at the Brillouin zone K-point). In order to eject such ele
 ctrons in vacuum and observe their dynamics\, a high energy (>20 eV) phot
 on source is required as well as ultrashort pulse\nduration. High Harmonic
  Generation source [1] combined to an Angle-Resolved PhotoEmission Spectr
 oscopy (ARPES) end-station is a powerful tool to observe such electron dy
 namics. After an introduction on ARPES and experimental concepts\, I will 
 present an overview of few recent time-resolved ARPES studies performed a
 t the Artemis facility. A quasi-free-standing monolayer of graphene (MLG)
  is optically excited in a direct interband regime. The measurement of th
 e electronic temperature reveals the role of the supercollisions during t
 he cooling process of the electrons [2]. Over ~100 fs\, a population\ninve
 rsion across the Dirac point is observed [3] supporting the potential of g
 raphene 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
 \ngive access to the direct quasiparticle band gap [4]. Depending on the s
 creening effects a strong band gap renormalization can be induced [5] by 
 optically excited free charge carriers. Control of spin- and valley-quant
 um numbers in valence and conduction bands is achieved [6-7] by using cir
 cularly polarized optical excitation.\n\n1. F. Frassetto et al.\, Optics E
 xpress 19\, 19169 (2011)           \n2. J. Johannsen et al.\, Phys R
 ev Lett 111\, 027403 (2013)     \n3. I. Gierz et al.\, Nature Materials
  12\, 1119 (2013)                  \n4. A. Grubišić Čabo et al
 .\, Nano Lett. 15\, 5883 (2015)\n5. S. Ulstrup et al.\, ACS Nano 10\, 6315
  (2016)\n6. S. Ulstrup et al.\, arXiv:1608.06023 (2016)\n7. R. Bertoni et 
 al.\, arXiv:1606.03218 (2016)\n 
LOCATION:CH G1 495 https://plan.epfl.ch/?room==CH%20G1%20495
STATUS:CONFIRMED
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