[seminar] Seminar na IF-u u četvrtak 10.09.2015. u 15:00h - Prof. Kazuya Watanabe (Kyoto)

[Damir Staresinic]

Institut za fiziku, Bijenička cesta 46, 

predavaonica u zgradi Mladen Paić četvrtak, 10. rujna 2015., u 15:00 sati 
  
Optical response of Cs intercalated graphene on Ir(111) 
Prof. Kazuya Watanabe 
  
Department of Chemistry, Kyoto University, Japan   

  


Epitaxial growth of graphene on transition metal surfaces has been known as a conventional method to obtain macroscopic high quality graphene sheet. On Ir(111), graphene can be prepared with an exceptionally high structural quality by a conventional chemical vapor deposition. Chemical doping by alkali atom intercalation between graphene and Ir substrate induces large shift of the Dirac point. While their electronic structures have been extensively investigated, their dynamical responses have been less explored. 
In this talk, we focus on Cs-intercalated graphene/Ir(111) and describe its peculiar optical response and ultrafast electron-phonon couplings revealed by steady state as well as femtosecond time-resolved reflectivity measurements. The Cs intercalation brings about a strong resonance feature in the optical reflectance spectra with a maximum reflectance change more than 10 % in visible region (2.1-2.2 eV). This giant response is possibly ascribed to a surface plasmon resonance of the Cs-intercalated graphene activated by a moire type periodic modulation of the graphene structure. In contrast to recent intensive researches on graphene plasmonics which mainly focus on far-infrared region, this indicates a possible strategy for pushing the resonance photon energy to visible region. In the pump-probe reflectivity measurement, a femtosecond laser pulse tuned to the resonance band induces time-domain oscillatory modulations of the resonance band. With a help of theoretical calculations, those oscillations are ascribed to coherent nuclear motions of intercalated Cs and graphene, and ultrafast couplings between the plasmonic excitation and surface nuclear motions are revealed.   

  

          
  
  
Voditelji seminara IF-a: Nataša Vujičić i Damir Starešinić 
  




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