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178 CHAPTER 7. CONCLUSION
although the energy gain of the superconducting wavefunction is small, and it is
difficult to get a definitive conclusion on the exact nature of the RVB phase. We
proposed additionally two other models that might shed light on the presence of
orbital currents: (1) We extended first the three-band Hubbard model by considering
the additional out-of-plane apical oxygens and the copper d 3z2−r2 orbitals,
(2) We considered an additional correlated hopping term in the three-band Hubbard
model. In the former model we found interestingly that when the transfer
integrals connected to the apical oxygen are slightly enhanced, then strong orbital
currents start to develop with an in-plane magnetic moment, in agreement
with neutron experimental results. In the latter model, we found that the orbital
currents are strongly stabilized when the correlated hopping V 2 ≈ 0.4. The symmetry
of the current pattern in this case is θ 2 like. Additionally, we have studied
further the orbital current present in the three-band Hubbard model when open
boundaries are considered. In this particular case, the flux flowing through the
boundary is removed, and the charge current phase is still stabilized. Finally,
it has also been argued that holes doped in the antiferromagnetically correlated
spin systems induce incommensurate spin correlations in the ground state for
the one-band hubbard model and three-band model within the mean-field approximation.
Therefore, it would be interesting to compare the energies of these
phases with our Jastrow projected wavefunction, and see if these phases are still
present.