Chemical pressure effect on the optical conductivity of the nodal-line semimetals ZrSi$Y$ ($Y$=S, Se, Te) and ZrGe$Y$ ($Y$=S, Te)

Abstract

ZrSiS is a nodal-line semimetal, whose electronic band structure contains a diamond-shaped line of Dirac nodes. We carried out a comparative study on the optical conductivity of ZrSiS and related compounds ZrSiSe, ZrSiTe, ZrGeS, and ZrGeTe by reflectivity measurements over a broad frequency range combined with density functional theory calculations. The optical conductivity exhibits a distinct U shape, ending at a sharp peak at around 10000~cm${}^{-1}$ for all studied compounds, except for ZrSiTe. The U shape of the optical conductivity is due to transitions between the linearly dispersing bands crossing each other along the nodal line. The sharp high-energy peak is related to transitions between almost parallel bands, and its energy position depends on the interlayer bonding correlated with the $c$/$a$ ratio, which can be tuned by either chemical or external pressure. For ZrSiTe, another pair of crossing bands appears in the vicinity of the Fermi level, corrugating the nodal-line electronic structure and leading to the observed difference in optical conductivity. The findings suggest that the Dirac physics in Zr$XY$ compounds with $X$=Si, Ge and $Y$=S, Se, Te is closely connected to the interlayer bonding.

arXiv comment9 pages, 6 figures

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• Nodal Semimetals: A Survey on Optical Conductivity
• Indications for Lifshitz transitions in the nodal-line semimetal ZrSiTe induced by interlayer interaction
• Dynamical conductivity in multiply-degenerate point-nodal semimetal CoSi
• Infrared spectroscopy study of the nodal-line semimetal candidate ZrSiTe under pressure: Hints for pressure-induced phase transitions
• Effect of mechanical strain on the optical properties of nodal-line semimetal ZrSiS
• Pressure-induced excitations in the out-of-plane optical response of the nodal-line semimetal ZrSiS
• Optical conductivity signatures of open Dirac nodal lines
• Evidence of 3D Dirac conical bands in TlBiSSe by optical and magneto-optical spectroscopy
• Signatures of van Hove singularities in the anisotropic in-plane optical conductivity of the topological semimetal Nb${}_3$SiTe${}_6$
• Dirac Nodal Line and Rashba Splitting Surface States in Nonsymmorphic ZrGeTe
• Strain Effects on Band Structure and Dirac Nodal-line Morphology of ZrSiSe
• Optical anisotropy of the kagome magnet FeSn: Dominant role of excitations between kagome and Sn layers
• In-plane and out-of-plane optical response of the nodal-line semimetals ZrGeS and ZrGeSe
• Polarization-dependent excitons and plasmon activity in nodal-line semimetal ZrSiS