We present a variational wave function for the ground state of the two
-dimensional spin-1/2 Heisenberg antiferromagnet. It is a modification
of a Monte Carlo variational wave function proposed by Huse and Elser
which gives excellent results for the ground-state energy but breaks
the rotational symmetry of the squared staggered magnetization. In the
ir case the x component of the squared staggered magnetization (m(x)(d
agger))(2) is much larger than (m(y)(dagger))(2) and (m(z)(dagger))(2)
, which are the y and z components, respectively. In this paper we sho
w how to restore the symmetry between m(x)(dagger) and m(y)(dagger). H
owever, m(z)(dagger) is still much smaller than m(x)(dagger). We also
study the enforcement of the full rotational symmetry in our trial wav
e function using only two spin interaction terms. Finally, we discuss
how errors in Monte Carlo data affect the efficiency of algorithms whi
ch determine more systematically the best variational parameters for t
he ground-state wave function.