Quantum criticality and minimal conductivity in graphene with long-range disorder |
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Authors: | Ostrovsky P M Gornyi I V Mirlin A D |
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Institution: | Institut für Nanotechnologie, Forschungszentrum Karlsruhe, 76021 Karlsruhe, Germany. |
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Abstract: | We consider the conductivity sigma of graphene with negligible intervalley scattering at half filling. We derive the effective field theory, which, for the case of a potential disorder, is a symplectic-class sigma model including a topological term with theta=pi. As a consequence, the system is at a quantum critical point with a universal value of the conductivity of the order of e(2)/h. When the effective time-reversal symmetry is broken, the symmetry class becomes unitary, and sigma acquires the value characteristic for the quantum Hall transition. |
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