Optical conductivity in multiferroic GaV4 S8 and GeV4 S8: Phonons and electronic transitions

S. Reschke, F. Mayr, Zhe Wang, P. Lunkenheimer, Weiwu Li, D. Szaller, S. Bordács, I. Kézsmárki, V. Tsurkan, A. Loidl

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

We report on optical spectroscopy on the lacunar spinels GaV4S8 and GeV4S8 in the spectral range from 100 to 23 000 cm-1 and for temperatures from 5 to 300 K. These multiferroic spinel systems reveal Jahn-Teller driven ferroelectricity and complex magnetic order at low temperatures. We study the infrared-active phonon modes and the low-lying electronic excitations in the cubic high-temperature phase, as well as in the orbitally and in the magnetically ordered low-temperature phases. We compare the phonon modes in these two compounds, which undergo different symmetry-lowering Jahn-Teller transitions into ferroelectric and orbitally ordered phases, and exhibit different magnetic ground states. We follow the splitting of the phonon modes at the structural phase transition and detect additional splittings at the onset of antiferromagnetic order in GeV4S8. We observe electronic transitions within the d-derived bands of the V4 clusters and document a significant influence of the structural and magnetic phase transitions on the narrow electronic band gaps.

Original languageEnglish
Article number144302
JournalPhysical Review B
Volume96
Issue number14
DOIs
Publication statusPublished - Oct 5 2017

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

Fingerprint Dive into the research topics of 'Optical conductivity in multiferroic GaV4 S8 and GeV4 S8: Phonons and electronic transitions'. Together they form a unique fingerprint.

  • Cite this

    Reschke, S., Mayr, F., Wang, Z., Lunkenheimer, P., Li, W., Szaller, D., Bordács, S., Kézsmárki, I., Tsurkan, V., & Loidl, A. (2017). Optical conductivity in multiferroic GaV4 S8 and GeV4 S8: Phonons and electronic transitions. Physical Review B, 96(14), [144302]. https://doi.org/10.1103/PhysRevB.96.144302