Holon pair condensation and phase diagram of high-Tc cuprates

A possibility of holon (boson) pair condensation is explored for hole-doped high-Tc cuprates, by using the U(1) slave-boson representation of the t-J Hamiltonian with the inclusion of hole-hole repulsion. A phase diagram of the hole doped high-Tc cuprates is deduced by allowing both the holon pairing and spinon pairing channels. It is shown that the spin gap size remains nearly unchanged below the holon pair condensation temperature. We find that the s-wave holon pairing under the condition of d-wave spin singlet pairing is preferred, thus allowing d-wave hole pairing.