  A normal (non-superconducting) ground state of the t-J model may be
variationally approximated by a Gutzwiller-projected wave function. Within this
approximation, at small hole doping near half-filling, the normal state favors
staggered-flux ordering. Such a staggered-flux state may occur in vortex cores
of underdoped high-temperature cuprate superconductors. From comparing the
energies of the staggered-flux state and of the superconducting state, we
numerically obtain the condensation energy. Extracting the superfluid density
directly from the projected superconducting wave function, we can also estimate
the coherence length at zero temperature.
