Conductivity of disordered graphene at half filling |
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Authors: | P M Ostrovsky I V Gornyi A D Mirlin |
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Institution: | 1.Institut für Nanotechnologie,Karlsruhe,Germany;2.Institut für Theorie der kondensierten Materie, Universit?t Karlsruhe,Karlsruhe,Germany |
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Abstract: | We study electron transport properties of a monoatomic graphite layer
(graphene) with different types of disorder at half filling. We show that the
transport
properties of the system depend strongly on the symmetry of disorder. We find
that the localization is ineffective if the randomness preserves one of the
chiral symmetries of
the clean Hamiltonian or does not mix valleys.
We obtain the exact value of minimal conductivity 4e2/πh in the case of
chiral disorder.
For long-range disorder (decoupled valleys), we derive the effective field
theory. In the case of smooth random potential, it is a
symplectic-class sigma-model including
a topological term with θ=π. As a consequence, the system is
at a quantum critical point with a universal value of the
conductivity of the order of e2/h. When the effective time reversal
symmetry is broken, the symmetry class becomes
unitary, and
the conductivity acquires the value characteristic for the quantum Hall transition. |
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Keywords: | |
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