Search for FQHE in graphene. John Watson, Sumit Mondal , Robert Niffenegger 4/29/09. Outline. Integer Quantum Hall Effect Semiconductor Graphene Fractional Quantum Hall Effect Theoretical Expectations for FQHE in Graphene Proposed Experiments Suspended Graphene
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John Watson, SumitMondal, Robert Niffenegger
2D Top View
Coupled Electrons and Magnetic Flux reduce Effective Magnetic field
[Papic et al. Arxiv:0902.3233v1]
(for example, in the ν = 2/3 case the valley unpolarized state is favored over the valley polarized states for both n = 0 and n = 1, Apalkov et al.)
The close lattice matching would introduce a mass term into the Dirac Hamiltonian which would lift the valley degeneracy of the zero energy Landau level
90 s buffered oxide etch
Bolotin, K.I. et al. Ultrahigh electron mobility in suspended graphene. Solid State Communications146, 351-355 (2008).
b: AFM of device
c: AFM after O2 plasma
High mobility sample on substrate
Li, G. et al. Scanning tunneling spectroscopy of graphene on graphite. Physical Review Letters102 (accepted April 2, 2009, unpublished as of April 28, 2009).
Larger separation between top & second layer
Differential tunneling conductance (proportional to DOS)
1Neugebauer, P. et al. How perfect can graphene be? arXiv 0903.1612v1 (2009).