Finite temperature spectral function of a hole in a quantum antiferromagnet and role of phonons

TL;DR

This paper investigates how finite temperature and phonons affect the spectral function of a hole in a 2D antiferromagnet, showing phonons broaden quasiparticle peaks but do not destroy string excitations, aligning well with ARPES data.

Contribution

It provides a detailed analysis of thermal and phononic effects on the hole spectral function in the t-J model, including vertex corrections, with improved agreement to experiments.

Findings

Phonons broaden the quasiparticle peak at finite temperature.

String excitations persist despite strong electron-phonon coupling.

Vertex corrections improve agreement with ARPES data with smaller coupling values.

Abstract

We study thermal broadening of the hole spectral function of the two-dimensional t-J model (and its extensions) within the non-crossing approximation with and without the contribution of optical phonons. We find that phonons at finite temperature broaden the lowest energy quasiparticle peak, however, the string excitations survive even for relatively strong electron-phonon coupling. Experimental angle resolved photo-emission spectroscopy(ARPES) results compare well with our calculations at finite temperature when we use strong electron-phonon coupling without any adhoc broadening. In addition, we have studied the role of vertex corrections and we find that their contribution allows us achieve the same overall agreement with the ARPES experimental results but using smaller values for the electron-phonon coupling.