Pseudogap and superconductivity in two-dimensional doped charge-transfer insulators

TL;DR

This study uses advanced computational methods to explore how doping a Mott insulator in a copper-oxide model leads to complex phase transitions, pseudogap phenomena, and superconductivity, revealing universal features of doped Mott insulators.

Contribution

It provides the first detailed phase diagram of a three-band charge-transfer model showing a first-order transition and Widom crossover line related to pseudogap and superconductivity.

Findings

First-order transition between pseudogap and correlated metal phases.

Presence of a Widom crossover line affecting thermodynamic properties.

Universal phase boundary features independent of microscopic details.

Abstract

High-temperature superconductivity emerges in the CuO$_2$ plane upon doping a Mott insulator. To ascertain the influence of Mott physics plus short-range correlations, we solve a three-band copper-oxide model in the charge-transfer regime using cellular dynamical mean-field theory with continuous-time quantum Monte Carlo as an impurity solver. We report the normal and superconducting phase diagram of this model as a function of doping, interaction strength and temperature. Upon hole doping of the charge-transfer insulator, the phase boundary between pseudogap and correlated metal consists of a first-order transition line at finite doping ending at a critical point, as in the one-band model. Beyond the endpoint, the phase boundary continues as a Widom crossover line, across which thermodynamic quantities peak. This phase boundary determines changes in the pairing mechanism and is an emergent phenomenon characteristic of doped Mott insulators, independent of many microscopic details. Broader implications are discussed.