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/

Zendy Plus

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

Zendy Tools

Zendy Open

We have investigated optical conductivity spectra of $n$- and $p$-typeBa$_8$Ga $_{16}$Sn$_{30}$ ($\alpha$-BGS) with type-VIII clathrate structure, attemperatures from 296\,K down to 6\,K with a terahertz time-domain spectrometer(0.2\,-\,2.5\,THz). The continuous spectra contributed from charge carriers aredispersive in this frequency range and also temperature- and carriertype-dependent. The Drude-Smith model taking multiple-scatterings of chargecarriers into account well reproduces those data. The relaxation rate of the$n$-type carriers decreases more sharply than that in the $p$-type material,suggesting that a stronger electron-phonon interaction may exist in the$n$-type than in the $p$-type. On the other hand, the localized infrared-activemodes observed at 1.3\,THz and 1.7\,THz, identified as the rattling phonons ofthe Ba$^{2+}$ ion's quasi-on-center vibrations, become soft and broadsignificantly with decreasing temperature as well as observed in type-I BGS andBGG (Ba$_8$Ga$_{16}$Ge$_{30}$) clathrates. The softening in the $n$-type issmaller by about 30% than in the $p$-type, whereas the linewidth brodening isalmost the same independently on the carrier type. The difference in thesoftening is discussed with a scenario where the interaction of rattlingphonons with carriers can modify the anharmonic potential of the guest ions.The anomalous broadening at low temepratures is also discussed by theimpurity-scattering model presented for a rattling-phonon system stronglyhybridized with acoustic cage phonons.

Optical conductivity spectra of the rattling phonons and charge carriers in type-VIII clathrate Ba$_8$Ga$_{16}$Sn$_{30}$