CRITERION FOR A GOOD VARIATIONAL WAVE-FUNCTION

The variance of the Hamiltonian in a given variational wave function measures how good an eigenstate this wave function is. In some instances, as for the two-dimensional antiferromagnetic Heisenberg Hamiltonian (2D AFH), the energy expectation value is not enough to distinguish between different trial Ansa$iuml tze. Here we propose the variance as a simple criterion, which allows for further differentiation between degenerate trial wave functions. We show that this criterion establishes the projected wave functions as candidates for the ground state of the 2D AFH. A strong interference effect is discovered in computer experiment. © 1990 The American Physical Society.