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SUMMARY:Electronic structure of graphene hybrid systems: impurities and in
 teractions
DTSTART:20131108T141500
DTSTAMP:20260924T071709Z
UID:8525511990b93475f663eb6bfcff4831301b43fb6944d1c2cc13a502
CATEGORIES:Conferences - Seminars
DESCRIPTION:Tim Wehlin\, Institute of Theoretical Physics\, Bremen Center 
 for Computational Materials Science\, University of Bremen\nGraphene combi
 nes ultimate two-dimensionality with a special electronic structure: it is
  a Dirac material\, which allows for strong doping and offers unprecedente
 d opportunities for chemical functionalization. Here\, we show how “Dira
 cness” determines the interaction of graphene with adatoms\, molecules\,
  and its response to electric fields.\nFirst\, resonant scatterers such as
  hydrogen adatoms can strongly enhance the low-energy density of states in
  graphene. We study the impact of these impurities on transport and electr
 onic screening and find a two-faced behavior: Kubo formula calculations re
 veal an increased dielectric function ε upon the creation of midgap state
 s but no metallic divergence at small momentum transfer q→0. A new lengt
 h scale beyond which screening is suppressed emerges\, which we identify w
 ith the Anderson localization length.\nAt increasing coverage interactions
  between the impurities emerge. We investigate how the interplay of deform
 ation energies and electronically mediated interactions affect the way imp
 urities arrange. We show that charge doping can trigger transitions betwee
 n several adsorbate phases.\nFinally\, the problem of Coulomb interactions
  in layered materials is addressed. Free standing graphene is shown to fea
 ture simultaneously strong local and non-local Coulomb interaction terms. 
 We demonstrate that the non-local Coulomb interactions are decisive for st
 abilizing the Dirac electron sea in graphene against instabilities towards
  strongly correlated phases.
LOCATION:PH L1 503 http://plan.epfl.ch/?room=PHL1503
STATUS:CONFIRMED
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