Tuesday, June 25, 2013

1306.5686 (S. Gattenloehner et al.)

Quantum Hall criticality and localization in graphene with short-range
impurities at the Dirac point

S. Gattenloehner, W. R. Hannes, P. M. Ostrovsky, I. V. Gornyi, A. D. Mirlin, M. Titov
We explore the longitudinal conductivity of graphene at the Dirac point in strong magnetic field with two types of short-range scatterers: adatoms that mix the valleys and "scalar" impurities that do not mix them. A scattering theory for the Dirac equation is employed to express the conductance of a graphene sample as a function of impurity coordinates; an averaging over positions of impurities is then performed numerically. The conductivity is equal to the ballistic value for each disorder realization provided the number of flux quanta considerably exceeds the number of impurities. For weaker fields, the conductivity in the presence of scalar impurities scales to the quantum-Hall critical point at half filling or to zero away from half filling due to the onset of Anderson localization. For adatoms the localization behavior is obtained also at half filling due to splitting of the critical energy by intervalley scattering. Our results reveal a complex scaling flow governed by fixed points of different symmetry classes.
View original: http://arxiv.org/abs/1306.5686

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