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Paper   IPM / Physic / 13112
School of Physics
  Title:   RKKY Interaction in Heavily Vacant Graphene
  Author(s): 
1.  A. Habibi
2.  S.A. Jafari
  Status:   Published
  Journal: J. Physics: Condens. Matter
  Vol.:  25
  Year:  2013
  Pages:   375501
  Supported by:  IPM
  Abstract:
Dirac electrons in clean graphene can mediate the interactions between two localized magnetic moments. The functional form of the RKKY interaction in pristine graphene is specified by two main features: (i) an atomic-scale oscillatory part determined by a wavevector Q connecting the two valleys; with doping another longer range oscillation appears which arises from the existence of an extended Fermi surface characterized by a momentum scale kF; (ii) an algebraic Rα decay in large distances where the exponent α = �?? 3 is a distinct feature of undoped Dirac sea in two dimensions. In this work, we investigate the effect of a few per cent vacancies on the above properties. Depending on the doping level, if the chemical potential lies on the linear part of the density of states, the exponent α remains at �??3 even in vacant graphene. Otherwise α reduces towards more negative values. Presence of vacancies washes out both atomic-scale and Friedel oscillations of the RKKY interaction. The absence of atomic-scale oscillations indicates the destruction of two-valley structure of the parent graphene material. However, the absence of Friedel oscillations upon 'alloying' with vacancies indicates that a quantum ground state of heavily vacant doped graphene is not given by a unique kF momentum scale.

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