# Projective Quasiparticle Interference of a Single Scatterer to Analyze the Electronic Band Structure of ZrSiS

## TL;DR

This paper introduces a projective quasiparticle interference (PQPI) method that enhances the analysis of electronic band structures in materials like ZrSiS by improving signal clarity along high-symmetry directions, revealing defect-dependent interactions.

## Contribution

The study presents a novel PQPI technique that increases signal-to-noise ratio in QPI measurements, enabling detailed analysis of defect-induced electronic scattering in complex materials.

## Key findings

- Resolved energy dispersions along high-symmetry directions.
- Observed defect-dependent scattering of bulk bands.
- Identified a new energy dispersion branch (q6).

## Abstract

Quasiparticle interference (QPI) of the electronic states has been widely applied in scanning tunneling microscopy (STM) to analyze the electronic band structure of materials. Single-defect induced QPI reveals defect-dependent interaction between a single atomic defect and electronic states, which deserves special attention. Due to the weak signal of single-defect-induced QPI, the signal-to-noise ratio (SNR) is relatively low in a standard two-dimensional QPI measurement. In this paper, we introduce a projective quasiparticle interference (PQPI) method, in which a one-dimensional measurement is taken along high-symmetry directions centered on a specified defect. We apply the PQPI method to a topological nodal-line semimetal ZrSiS. We focus on two special types of atomic defects that scatter the surface and bulk electronic bands. With enhanced SNR in PQPI, the energy dispersions are clearly resolved along high symmetry directions. We discuss the defect-dependent scattering of bulk bands with the non-symmorphic symmetry-enforced selection rules. Furthermore, an energy shift of the surface floating band is observed and a new branch of energy dispersion (q6) is resolved. This PQPI method can be applied to other complex materials to explore defect-dependent interactions in the future.