Electronic dispersion anomalies in the iron pnictide superconductor Ba_{1-x}K_xFe_2As_2

TL;DR

This paper develops a model of electron interactions with magnetic excitations in Ba_{1-x}K_xFe_2As_2, explaining experimental spectra and supporting a spin-fluctuation-mediated pairing mechanism in iron pnictide superconductors.

Contribution

It introduces a temperature-dependent magnetic excitation model that accurately reproduces experimental ARPES and tunnelling spectra, highlighting the role of spin fluctuations in pairing.

Findings

Quantitative agreement with experimental spectra

Estimated electron-spin excitation coupling strength

Supported spin-fluctuation pairing mechanism

Abstract

The pairing mechanism in the iron-pnictide superconductors is still unknown. However, similarities to the cuprate high-temperature superconductors suggest that a similar mechanism may be at work. Recently, careful experimental studies of the spin excitation spectrum revealed, like in the cuprates, a strong temperature dependence in the normal state and a resonance feature in the superconducting state. Motivated by these findings, we develop a model of electrons interacting with a temperature dependent magnetic excitation spectrum based on these experimental observations. We apply it to analyse angle resolved photoemission and tunnelling spectra in Ba{1-x}KxFe2As2. We reproduce in quantitative agreement with experiment a renormalisation of the quasiparticle dispersion both in the normal and the superconducting state, and the dependence of the quasiparticle linewidth on binding energy. We estimate the strength of the coupling between electronic and spin excitations. Our findings support the possibility of a pairing mechanism based dominantly on such a coupling.