title: Universal quantized spin-Hall conductance fluctuation in graphene.
abstract: We report theoretical investigations of the quantized spin-Hall conductance fluctuation of graphene in the presence of disorder. Two graphene models that exhibit the quantized spin-Hall effect (QSHE) are analyzed. Model I is with unitary symmetry under an external magnetic field B not = 0 but with a zero spin-orbit interaction, t(SO)=0. Model II is with symplectic symmetry where B=0 but t(SO) not = 0. The two models give exactly the same universal QSHE conductance fluctuation value 0.285+/-0.005e/4pi regardless of symmetry. We also examined a third model that exhibits QSHE but with quadratic dispersion and obtained the same results. Finally, all three models of QSHE have a one-sided log-normal distribution for spin-Hall conductance. Our results strongly suggest that the quantized spin-Hall conductance fluctuation belongs to a new universality class.
authors.affiliation: Department of Physics and the Center of Theoretical and Computational Physics, The University of Hong Kong, Hong Kong, China.
authors.forename: Zhenhua
authors.initials: Z
authors.lastname: Qiao
authors.forename: Jian
authors.initials: J
authors.lastname: Wang
authors.forename: Yadong
authors.initials: Y
authors.lastname: Wei
authors.forename: Hong
authors.initials: H
authors.lastname: Guo