Spectral evolution with doping of an antiferromagnetic Mott state

TL;DR

This study investigates how doping affects the spectral properties of an antiferromagnetic Mott insulator using advanced numerical methods, revealing in-gap states that evolve with doping and relate to Coulomb interactions.

Contribution

It introduces a diagonalization approach on top of VMC to analyze spectral evolution in doped Mott insulators, aligning theoretical results with recent experimental observations.

Findings

In-gap states appear with doping, consistent with STS experiments.

In-gap states gain spectral weight from the upper Hubbard band.

The energy scale of in-gap states relates to Coulomb interaction U.

Abstract

Since the discovery of half-filled cuprate to be a Mott insulator, the excitation spectra above the chemical potential for the unoccupied states has attracted many research attentions. There were many theoretical works using different numerical techniques to study this problem, but many have reached different conclusions. One of the reasons is the lack of very detailed high-resolution experimental results for the theories to be compared with. Recently, the scanning tunneling spectroscopy (STS)\cite{cai2015visualizing,ye2013visualizing} on lightly doped Mott insulator with an antiferromagnetic (AFM) order found the presence of in-gap states with energy of order half an eV above the chemical potential. The measured spectral properties with doping are not quite consistent with earlier theoretical works. In this paper we perform a diagonalization method on top of the variational Monte Carlo (VMC) calculation to study the evolution of AFM Mott state with doped hole concentration in the Hubbard model (HM). Our results found in-gap states that behave similarly with ones reported by STS. These in-gap states acquire a substantial amount of dynamical spectral weight transferred from the upper Hubbard band. The in-gap states move toward chemical potential with increasing spectral weight as doping increases. Our result also provides information about the energy scale of these in-gap states in relation with the coulomb coupling strength U.