Termination Dependent Topological Surface States in Nodal Loop Semimetal HfP2

TL;DR

This paper reports the experimental observation of termination-dependent topological surface states in the nodal loop semimetal HfP2, revealing the role of symmetry in protecting these states and expanding understanding of topological materials.

Contribution

First experimental detection of topological surface states in HfP2, supported by calculations, highlighting the influence of termination and nonsymmorphic symmetry in topological protection.

Findings

Surface states linked to three nodal loops are topologically non-trivial.

Surface states depend on the termination of the crystal.

Transition metal dipnictides are promising platforms for topological studies.

Abstract

Symmetry plays a major role in all disciplines of physics. Within the field of topological materials there is a great interest in understanding how the mechanics of crystalline and internal symmetries protect crossings between the conduction and valence bands. Additionally, exploring this direction can lead to a deeper understanding on the topological properties of crystals hosting a variety of symmetries. For the first time, we report the experimental observation of topological surface states in the nodal loop semimetal HfP2 using angle resolved photoemission spectroscopy (ARPES) which is supported by our first principles calculations. Our study shows termination dependent surface states in this compound. Our experimental data reveal surface states linked to three unique nodal loops confirmed by theoretical calculation to be topologically non-trivial. This work demonstrates that transition metal dipnictides provide a good platform to study non-trivial topological states protected by nonsymmorphic symmetry.