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 kz=0 and kz=π electronic states. This result unifies both tunnelling and photoemission based experiments on FeSe and highlights the importance of kz within surface sensitive measurements of QPI.
@article{arxiv.1906.02150,
title = {$k_z$ selective scattering within Quasiparticle Interference measurements of FeSe},
author = {Luke C. Rhodes and Matthew D. Watson and Timur K. Kim and Matthias Eschrig},
journal= {arXiv preprint arXiv:1906.02150},
year = {2019}
}