$k_z$ selective scattering within Quasiparticle Interference measurements of FeSe

TL;DR

This study reveals that quasiparticle interference measurements in FeSe capture all electronic states with negligible group velocity in the z-axis, emphasizing the importance of three-dimensional electronic structure in surface-sensitive QPI data.

Contribution

It demonstrates that QPI data in FeSe include all relevant electronic states with minimal z-axis group velocity, integrating 3D electronic structure into surface-sensitive measurements.

Findings

QPI data in FeSe include all states with negligible z-axis group velocity.

A 3D tight-binding model reproduces experimental QPI dispersion.

Highlights the significance of k_z in surface-sensitive QPI measurements.

Abstract

Quasiparticle interference (QPI) provides a wealth of information relating to the electronic structure of a material. However, it is often assumed that this information is constrained to two-dimensional electronic states. Here, we show that this is not necessarily the case. For FeSe, a system dominated by surface defects, we show that it is actually all electronic states with negligible group velocity in the $z$ axis that are contained within the experimental data. By using a three-dimensional tight binding model of FeSe, fit to photoemission measurements, we directly reproduce the experimental QPI scattering dispersion, within a T-matrix formalism, by including both $k_z = 0$ and $k_z = \pi$ electronic states. This result unifies both tunnelling and photoemission based experiments on FeSe and highlights the importance of $k_z$ within surface sensitive measurements of QPI.