  The Kugel-Khomskii model, the simplest model for orbital degenerate magnetic
insulators, exhibits a zero temperature degeneracy in the classical limit which
could cause genuine quantum disorder. Khaliullin and Oudovenko [Phys. Rev. B
56, R14 243 (1997)] suggested recently that instead a particular classical
state could be stabilized by quantum fluctuations. Here we compare their
approach with standard random phase approximation and show that it strongly
underestimates the strength of the quantum fluctuations, shedding doubts on the
survival of any classical state.

Strongly Correlated Electrons