Spin polaron damping in the spin-fermion model for cuprate superconductors

TL;DR

This paper develops a self-consistent Green's function approach to study spin polaron excitations in the spin-fermion model for cuprates, revealing spectral features consistent with experimental photoemission data.

Contribution

It introduces a novel self-consistent, spin rotational invariant method to calculate spectral functions and lifetimes of spin polarons in the cuprate model.

Findings

Pronounced quasiparticle peak near (pi/2,pi/2)

Absence of quasiparticle at Gamma-point

Spectral asymmetry consistent with experiments

Abstract

A self-consistent, spin rotational invariant Green's function procedure has been developed to calculate the spectral function of carrier excitations in the spin-fermion model for the CuO2 plane. We start from the mean field description of a spin polaron in the Mori-Zwanzig projection method. In order to determine the spin polaron lifetime in the self-consistent Born approximation, the self-energy is expressed by an irreducible Green's function. Both, spin polaron and bare hole spectral functions are calculated. The numerical results show a well pronounced quasiparticle peak near the bottom of the dispersion at (pi/2,pi/2), the absence of the quasiparticle at the Gamma-point, a rather large damping away from the minimum and an asymmetry of the spectral function with respect to the antiferromagnetic Brillouin zone. These findings are in qualitative agreement with photoemission data for undoped cuprates. The direct oxygen-oxygen hopping is responsible for a more isotropic minimum at (pi/2,pi/2).