Non-rigid hole band in the extended t-J model

TL;DR

This paper investigates the dispersion of a single hole in an extended t-J model with additional hopping and frustration, revealing results consistent with experimental observations in cuprates.

Contribution

It introduces a combined methodological approach and demonstrates how frustration and doping effects alter the hole dispersion in cuprates.

Findings

Isotropic minimum at (π/2,π/2) matches experimental data

Frustration induces flat regions and saddle points in dispersion

Results align with ARPES observations in cuprates

Abstract

The dispersion of one hole in an extended $t$-$J$ model with additional hopping terms to second and third nearest neighbours and a frustration term in the exchange part has been investigated. Two methods, a Green's function projection technique describing a magnetic polaron of minimal size and the exact diagonalization of a $4*4$ lattice, have been applied, showing reasonable agreement among each other. Using additional hopping integrals which are characteristic for the CuO$_2$ plane in cuprates we find in the nonfrustrated case an isotropic minimum of the dispersion at the point $(\pi/2,\pi/2)$ in $k$-space in good coincidence with recent angle-resolved photoemission results for the insulating compound Sr$_2$CuO$_2$Cl$_2$. Including frustration or finite temperature which shall simulate the effect of doping, the dispersion is drastically changed such that a flat region and an extended saddle point may be observed between $(\pi/2,0)$ and $(\pi,0)$ in agreement with experimental results for the optimally doped cuprates.