Long-range spin correlations in a honeycomb spin model with magnetic field

A. V. Lunkin, K. S. Tikhonov, M. V. Feigel'man

We consider spin-$\frac{1}{2}$ model on the honeycomb lattice in the presence of weak magnetic field $h\ll J$. Such a perturbation treated in the second order over $h$ leads to the…