Mott transition in cuprate high-temperature superconductors

In this study, we investigate the metal-insulator transition of charge transfer type in high-temperature cuprates. We first show that we must introduce a new band parameter in the three-band d-p model to reproduce the Fermi surface of high temperature cuprates such as BSCCO, YBCO and Hg1201. We present a new wave function of a Mott insulator based on the improved Gutzwiller function, and show that there is a transition from a metal to a charge-transfer insulator for such parameters by using the variational Monte Carlo method. This transition occurs when the level difference ${\mathrm{\Delta }}_{dp}\equiv {ϵ}_p-{ϵ}_d$ between d and p orbitals reaches a critical value $({\mathrm{\Delta }}_{dp}{)}_c$. The energy gain $\mathrm{\Delta }E$, measured from the limit of large ${\mathrm{\Delta }}_{dp}$, is proportional to $1\mathrm{/}{\mathrm{\Delta }}_{dp}$ for ${\mathrm{\Delta }}_{dp}>({\mathrm{\Delta }}_{dp}{)}_c$: $\mathrm{\Delta }E\propto -t_{dp}^2\mathrm{/}{\mathrm{\Delta }}_{dp}$. We obtain $({\mathrm{\Delta }}_{dp}{)}_c\simeq 2t_{dp}$ using the realistic band parameters.