Hubbard Fermi surface in the doped paramagnetic insulator

TL;DR

This study uses finite temperature Quantum Monte-Carlo simulations to analyze the electronic structure of doped paramagnetic insulators in the 2D Hubbard model, revealing how doping affects the Fermi surface and spectral properties.

Contribution

It provides detailed insights into the evolution of the Fermi surface and spectral weight transfer in the doped 2D Hubbard model at finite temperature, comparing results with theoretical predictions.

Findings

Doping causes a rigid shift of the chemical potential into the lower Hubbard band.

Luttinger theorem is violated for hole dopings less than 20%.

Fermi surface topology matches Hubbard I approximation predictions.

Abstract

We study the electronic structure of the doped paramagnetic insulator by finite temperature Quantum Monte-Carlo simulations for the 2D Hubbard model. Throughout we use the moderately high temperature T=0.33t, where the spin correlation length has dropped to < 1.5 lattice spacings, and study the evolution of the band structure with hole doping. The effect of doping can be best described as a rigid shift of the chemical potential into the lower Hubbard band, accompanied by some transfer of spectral weight. For hole dopings <20% the Luttinger theorem is violated, and the Fermi surface volume, inferred from the Fermi level crossings of the `quasiparticle band', shows a similar topology and doping dependence as predicted by the Hubbard I and related approximations.