Comparison of 32-site exact diagonalization results and ARPES spectral functions for the AFM insulator $Sr_2CuO_2Cl_2$

TL;DR

This study compares exact diagonalization results with ARPES spectral functions for Sr2CuO2Cl2, showing that a refined one-band t-J model can explain key spectral features and quasiparticle properties.

Contribution

It demonstrates that an extended one-band t-J model with specific hopping terms accurately reproduces spectral functions and quasiparticle lifetimes in a prototypical AFM insulator.

Findings

Extended t-J model matches spectral dispersion.

Energy-dependent broadening accounts for incoherent spectral parts.

Discrepancies near k = (π/2,0) suggest model limitations.

Abstract

We explore the success of various versions of the one-band t-J model in explaining the full spectral functions found in angle-resolved photoemission spectra for the prototypical, quasi two-dimensional, tetragonal, antiferromagnetic insulator $Sr_2CuO_2Cl_2$. After presenting arguments justifying our extraction of $A(k,\omega)$ from the experimental data, we rely on exact-diagonalization results from studies of a square 32-site lattice, the largest cluster for which such information is presently available, to perform this comparison. Our work leads us to believe that (i) a one-band model that includes hopping out to third-nearest neighbours, as well three-site, spin-dependent hopping, can indeed explain not only the dispersion relation, but also the quasiparticle lifetimes -- only in the neighbourhood of $k = (\pi/2,0)$ do we find disagreement; (ii) an energy-dependent broadening function, $\Gamma (E) = \Gamma_0 + A E$, is important in accounting for the incoherent contributions to the spectral functions.