Doping dependence of ordered phases and emergent quasiparticles in the doped Hubbard-Holstein model

TL;DR

This study uses quantum Monte Carlo simulations to explore how doping affects phases and quasiparticles in the Hubbard-Holstein model, revealing suppression of insulating states and emergence of metallic behavior with potential superconductivity.

Contribution

It provides new insights into the doping-dependent phase transitions and quasiparticle emergence in the Hubbard-Holstein model using determinant quantum Monte Carlo methods.

Findings

Mott insulator state is quickly suppressed upon doping.

Peierls insulator persists at higher doping levels.

d-wave superconducting susceptibility increases at lower temperatures.

Abstract

We present determinant quantum Monte Carlo simulations of the hole-doped single-band Hubbard-Holstein model on a square lattice, to investigate how quasiparticles emerge when doping a Mott insulator (MI) or a Peierls insulator (PI). The MI regime at large Hubbard interaction $U$ and small relative electron-phonon coupling strength $\lambda$ is quickly suppressed upon doping, by drawing spectral weight from the upper Hubbard band and shifting the lower Hubbard band towards the Fermi level, leading to a metallic state with emergent quasiparticles at the Fermi level. On the other hand, the PI regime at large $\lambda$ and small $U$ persists out to relatively high doping levels. We study the evolution of the $d$-wave superconducting susceptibility with doping, and find that it increases with lowering temperature in a regime of intermediate values of $U$ and $\lambda$.