Topological surface electronic states in candidate nodal-line semimetal CaAgAs

TL;DR

This study combines experimental and theoretical methods to reveal topological surface states in CaAgAs, confirming its status as a nodal-line semimetal with nontrivial topology and p-doping effects.

Contribution

It provides the first combined experimental and theoretical evidence of topological surface states in CaAgAs, a candidate nodal-line semimetal.

Findings

Observation of a non-$k_z$-dispersive surface band matching topological surface states.

Experimental Fermi level downshift indicating p-doping due to Ag vacancies.

Confirmation of the topological nontriviality of CaAgAs.

Abstract

We investigate systematically the bulk and surface electronic structure of the candidate nodal-line semimetal CaAgAs by angle resolved photoemission spectroscopy and density functional calculations. We observed a metallic, linear, non-$k_z$-dispersive surface band that coincides with the high-binding-energy part of the theoretical topological surface state, proving the topological nontriviality of the system. An overall downshift of the experimental Fermi level points to a rigid-band-like $p$-doping of the samples, due possibly to Ag vacancies in the as-grown crystals.