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The orbital diamagnetic susceptibility is calculated in monolayer and bilayer graphenes with band gap as well as in three-dimensional Dirac systems. It is demonstrated that the pseudospin degree of freedom such as valleys produces paramagnetic susceptibility analogous to contribution from real spin, and it dominates over the Landau diamagnetism. The pseudospin paramagnetism explains the origin of a singular diamagnetism which is present only in the band-gap region and disappears rapidly inside the conduction and valence bands.
Koshino et al. (Tue,) studied this question.