Resonating valence bond states in doped square-lattice antiferromagnets: finite cluster calculations

We discuss some general features of the resonating valence bond (RVB) ansatz for the ground state of quantums=1/2 Heisenberg antiferromagnets (AFMs). For finite clusters of up to 16 spins on the square lattice we compare the exact ground state with a short-range correlated RVB trial wave function. Since in the pure square-lattice AFM the short-range correlated RVB state differs significantly from the real ground state we discuss different mechanisms that favour the RVB state. In particular, we study the influence of anisotropy, disorder and frustration, which could be relevant for slightly doped high-T _c superconducting materials. Furthermore, we discuss the influence of holes on the realization of a RVB state. We found that exchange disorder and, in particular, frustration and holes can favour a short-range correlated magnetic state, which is well described by a RVB state.