Fermi surface and effective masses in photoemission response of the (Ba$_{1-x}$K$_x$)Fe$_2$As$_2$ superconductor

TL;DR

This study combines experimental and theoretical ARPES analysis of (Ba$_{1-x}$K$_x$)Fe$_2$As$_2$, clarifying spectral features, the Lifshitz transition, and the extrinsic effects influencing effective mass measurements, especially at different photon energies.

Contribution

It provides a comprehensive explanation of ARPES features in this superconductor and highlights the extrinsic influence on effective mass determination, improving interpretation of ARPES data.

Findings

Identification of the origin of ARPES spectral features.

Demonstration of the impact of final state effects on ARPES spectra.

Soft-X-ray ARPES yields more accurate effective mass values.

Abstract

The angle-resolved photoemission spectra of the superconductor (Ba$_{1-x}$K$_x$)Fe$_2$As$_2$ have been investigated both experimentally and theoretically. Our results explain the previously obscured origins of all salient features of the ARPES response of this paradigm pnictide compound and reveal the origin of the Lifshitz transition. Comparison of calculated ARPES spectra with the underlying DMFT band structure shows an important impact of final state effects, which results for three-dimensional states in a deviation of the ARPES spectra from the true spectral function. In particular, the apparent effective mass enhancement seen in the ARPES response is not an entirely intrinsic property of the quasiparticle valence bands but may have a significant extrinsic contribution from the photoemission process and thus differ from its true value. Because this effect is more pronounced for low photoexcitation energies, soft-X-ray ARPES delivers more accurate values of the mass enhancement due to a sharp definition of the 3D electron momentum.