Unconventional Integer Quantum Hall effect in graphene

We demonstrate that the band structure of graphene, where the low-energy dynamic of quasiparticles is described by 2+1 dimensional Dirac theory, produces an unconventional form of the quantized Hall conductivity $\sigma_{xy} = - (4 e^2/h)(n+1/2)$ with $n=0,1,...$. This remarkable effect is caused by the quantum anomaly of the $n=0$ Landau level and it is observed in recent experiments on thin graphene films.