Intermediate-Coupling Theory for the Spectral Weight of Spin Polaron

TL;DR

This paper develops an intermediate-coupling theory to analyze the spectral weight of a spin polaron, revealing its limitations at low exchange interaction ratios and comparing it with self-consistent calculations.

Contribution

It introduces an intermediate-coupling theoretical framework for the quasiparticle weight of a spin polaron and assesses its validity range.

Findings

The quasiparticle weight Z is finite at the band minimum for certain momenta.

The intermediate-coupling theory is valid only when J/t ≥ 1.6.

The approach fails at small J, and the reasons are explained.

Abstract

Within the intermediate-coupling theory, the quasiparticle weight $Z$ of one hole injected in the undoped antiferromagnetic ground state is studied. We find that, for the hole located at the quasiparticle band minimun with momentum ${\bf k}_0 = (\pm \frac{\pi}{2}, \pm \frac{\pi}{2})$, $Z$ is finite. By comparing the results obtained by the self-consistent Born approximation, we show that the intermediate-coupling theory for $Z$ is appropriate only when $J/t \stackrel{>}{\sim} 1.6$. Finally, the reason why this approach fails in the small-$J$ case will also be clarified.