Phase diagram of the frustrated spin-1/2 Heisenberg antiferromagnet in 2 dimensions

Abstract

Using a Lanczos technique we study the frustrated spin-(1/2 Heisenberg model on square lattices of 16 and 20 sites. Frustration is introduced by an interaction along the diagonals of the plaquettes with coupling ${J}_{2}$\ensuremath{\ge}0. For large ${J}_{2}$ we found that the ground state breaks (spontaneously) the lattice rotational symmetry. For intermediate values of ${J}_{2}$, the squares of order parameters associated with spin-Peierls and ``twisted'' states have a peak while a similar quantity for a chiral state shows no interesting structure.