# Impurity-induced resonant states in topological nodal-line semimetals

## TL;DR

This paper theoretically investigates impurity effects in topological nodal-line semimetals, revealing robust surface impurity states linked to topological surface states, which can be detected via scanning tunneling microscopy.

## Contribution

It provides a theoretical analysis of impurity-induced states in topological nodal-line semimetals, highlighting the robustness of surface impurity states due to topological protection.

## Key findings

- Surface impurity states are robust across a wide range of potentials.
- Bulk impurities can induce in-gap states near the impurity site.
- Surface impurity states can be probed by scanning tunneling microscopy.

## Abstract

Nodal-line semimetals are characterized by a kind of topologically nontrivial bulk-band crossing, giving rise to almost flat surface states. Yet, a direct evidence of the surface states is still lacking. Here we study theoretically impurity effects in topological nodal-line semimetals based on the T-matrix method. It is found that for a bulk impurity, some in-gap states may be induced near the impurity site, while the visible resonant impurity state can only exist for certain strength of the impurity potentials. For a surface impurity, robust resonant impurity states exist in a wide range of impurity potentials. Such robust resonant states stem from the topological protected weak dispersive surface states, which can be probed by scanning tunneling microscopy, providing a strong signature of the topological surface states in the nodal-line semimetals.