Surface floating 2D bands in layered nonsymmorphic semimetals: ZrSiS and related compounds

TL;DR

This paper models the surface states in nonsymmorphic semimetals, revealing floating 2D bands that differ from known surface states, supported by DFT and ARPES data, with implications for related materials.

Contribution

It introduces a new model for surface states in nonsymmorphic semimetals, explaining the origin of floating 2D bands and their dependence on surface conditions.

Findings

Identification of floating 2D surface bands in ZrSiS

Agreement between DFT calculations and ARPES measurements

Surface chemical potential influences surface density of states

Abstract

In this work, we present a model of the surface states of nonsymmorphic semimetals. These are derived from surface mass terms that lift the high degeneracy imposed in the band structure by the nonsymmorphic bulk symmetries. Reflecting the reduced symmetry at the surface, the bulk bands are strongly modified. This leads to the creation of two-dimensional floating bands, which are distinct from Shockley states, quantum well states or topologically protected surface states. We focus on the layered semimetal ZrSiS to clarify the origin of its surface states. We demonstrate an excellent agreement between DFT calculations and ARPES measurements and present an effective four-band model in which similar surface bands appear. Finally, we emphasize the role of the surface chemical potential by comparing the surface density of states in samples with and without potassium coating. Our findings can be extended to related compounds and generalized to other crystals with nonsymmorphic symmetries.