In-plane and out-of-plane optical response of the nodal-line semimetals ZrGeS and ZrGeSe

Abstract

Polarization-dependent reflectivity measurements were carried out over a broad frequency range on single-crystalline ZrGeSe and ZrGeS compounds, which are closely related to the prototype nodal-line semimetal ZrSiS. These measurements revealed the strongly anisotropic character of both ZrGeSe and ZrGeS, with a reduced plasma frequency for the out-of-plane direction {\bf E}$\Vert c$ as compared to the in-plane direction {\bf E}$\Vert ab$. For {\bf E}$\Vert ab$ the optical conductivity spectrum consists of two Drude terms followed by a shoulder or plateau-like behavior and a distinct U shape at higher energies, while for {\bf E}$\Vert c$ one Drude term is followed by a peak-like behavior and the U shape of the profile is less developed. Under external pressure, two prominent excitations appear in the out-of-plane optical conductivity spectrum of ZrGeSe, whose frequency position and oscillator strength show a weak anomaly at $\sim$3~GPa. Overall, the pressure-induced changes in the profile of the {\bf E}$\Vert c$ conductivity spectrum are much enhanced above $\sim$3~GPa. We compare our results to those recently reported for ZrSiS in a quantitative manner.

8 pages, 6 figures, accepted for publication in Phys. Rev. B

References in corpus (7)

• Use of X-ray scattering functions in Kramers-Kronig analysis of reflectance
• Non-symmorphic band degeneracy at the Fermi level in ZrSiTe
• Flat optical conductivity in ZrSiS due to two-dimensional Dirac bands
• Pressure-induced deconfinement of the charge transport in the quasi-one-dimensional Mott insulator (TMTTF)_2AsF_6
• Chemical pressure effect on the optical conductivity of the nodal-line semimetals ZrSi$Y$ ($Y$=S, Se, Te) and ZrGe$Y$ ($Y$=S, Te)
• Infrared spectroscopy study of the nodal-line semimetal candidate ZrSiTe under pressure: Hints for pressure-induced phase transitions
• Pressure-induced excitations in the out-of-plane optical response of the nodal-line semimetal ZrSiS

Cited by in corpus (3)

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• Near room-temperature ferromagnetism from double-exchange in the van der Waals material CrGeTe${}_3$: evidence from optical conductivity under pressure