Terahertz Dielectric Analysis and Spin-Phonon Coupling in Multiferroic GeV${}_4$S${}_8$

Abstract

We present an investigation of the multiferroic lacunar spinel compound GeV${}_4$S${}_8$ using time-domain terahertz spectroscopy. We find three absorptions which either appear or shift at the antiferromagnetic transition temperature, T${}_N=17$ K, as S=1 magnetic moments develop on vanadium tetrahedra. Two of these absorptions are coupled to the magnetic state and one only appears below the Néel temperature, and is interpreted as a magnon. We also observe isosbestic points in the dielectric constant in both the temperature and frequency domains. Further, we perform analysis on the isosbestic features to reveal an interesting collapse into a single curve as a function of both frequency and temperature, behavior which exists throughout the phase transitions. This analysis suggests the importance of spectral changes in the terahertz range which are linear in frequency and temperature.

arXiv comment7 pages, 4 figures. V2 in response to referees

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Cited by in corpus (7)

• Optical conductivity in multiferroic GaV${}_4$S${}_8$ and GeV${}_4$S${}_8$: Phonons and electronic transitions
• Sub-gap optical response across the structural phase transition in van der Waals layered α-RuCl${}_3$
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• Ring-Exchange Interaction Effects on Magnons in Dirac Magnet CoTiO${}_3$
• Robust cycloid crossover driven by anisotropy in the skyrmion host GaV${}_4$S${}_8$
• Broadband Circular Polarization Time-Domain Terahertz Spectroscopy
• Spin dynamics in the skyrmion-host lacunar spinel GaV4S8