Observation of bulk nodal lines in topological semimetal ZrSiS

TL;DR

This study uses bulk-sensitive soft X-ray ARPES to directly observe multiple three-dimensional bulk nodal lines in ZrSiS, confirming its status as a topological nodal-line semimetal with carriers entirely from nodal-line fermions.

Contribution

First direct bulk observation of multiple 3D nodal lines in ZrSiS using soft X-ray ARPES, clarifying its electronic structure beyond surface state measurements.

Findings

Identification of two groups of 3D bulk nodal lines

Nodal lines on high-symmetry planes are at the Fermi level

Carriers are entirely contributed by nodal-line fermions

Abstract

ZrSiS is the most intensively studied topological nodal-line semimetal candidate, which is proposed to host multiple nodal lines in its bulk electronic structure. However, previous angle-resolved photoemission spectroscopy (ARPES) experiments with vacuum ultraviolet lights mainly probed the surface states. Here using bulk-sensitive soft X-ray ARPES, we acquire the bulk electronic states of ZrSiS without any interference from surface states. Our results clearly show two groups of three-dimensional bulk nodal lines located on high-symmetry planes and along high-symmetry lines in the bulk Brillouin zone, respectively. The nodal lines on high-symmetry planes are enforced to pin at the Fermi level by carrier compensation and constitute the whole Fermi surfaces. This means that the carriers in ZrSiS are entirely contributed by nodal-line fermions, suggesting that ZrSiS is a remarkable platform for studying physical properties related to nodal lines.