English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We report on optical spectroscopy on the lacunar spinels GaV$_4$S$_8$ andGeV$_4$S$_8$ in the spectral range from 100 to 23000 cm$^{-1}$ and fortemperatures from 5 to 300 K. These multiferroic spinel systems revealJahn-Teller driven ferroelectricity and complex magnetic order at lowtemperatures. We study the infrared-active phonon modes and the low-lyingelectronic excitations in the cubic high-temperature phase, as well as in theorbitally and in the magnetically ordered low-temperature phases. We comparethe phonon modes in these two compounds, which undergo differentsymmetry-lowering Jahn-Teller transitions into ferroelectric and orbitallyordered phases, and exhibit different magnetic ground states. We follow thesplitting of the phonon modes at the structural phase transition and detectadditional splittings at the onset of antiferromagnetic order in GeV$_4$S$_8$.We observe electronic transitions within the $d$-derived bands of the V$_4$clusters and document a significant influence of the structural and magneticphase transitions on the narrow electronic band gaps.

Optical conductivity in multiferroic GaV$_4$S$_8$ and GeV$_4$S$_8$: Phonons and electronic transitions