Mott transition in cuprate high-temperature superconductors

TL;DR

This paper investigates the Mott transition in high-temperature cuprate superconductors, introducing a new band parameter in the three-band model and demonstrating a transition from metal to charge-transfer insulator via variational Monte Carlo methods.

Contribution

It introduces a new band parameter in the three-band model and presents a wave function for Mott insulators, identifying the critical level difference for the transition.

Findings

Transition occurs at a critical level difference $(\Delta_{dp})_c \\simeq 2t_{dp}$

Energy gain scales as $-t_{dp}^2/\\Delta_{dp}$ beyond the critical point

A new wave function for Mott insulators is proposed

Abstract

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 $\Delta_{dp}\equiv \epsilon_p-\epsilon_d$ between d and p orbitals reaches a critical value $(\Delta_{dp})_c$. The energy gain $\Delta E$, measured from the limit of large $\Delta_{dp}$, is proportional to $1/\Delta_{dp}$ for $\Delta_{dp}>(\Delta_{dp})_c$: $\Delta E\propto -t_{dp}^2/\Delta_{dp}$. We obtain $(\Delta_{dp})_c\simeq 2t_{dp}$ using the realistic band parameters.