Effect of magnetism and phonons on localized carriers in the ferrimagnetic kagome metals GdMn6Sn6 and TbMn6Sn6

Kagome metals possess peculiar optical spectra consisting of contributions from free charge carriers in a Drude-type response, localized carriers seen as a strongly temperature-dependent localization peak, and, in some cases, phonons displaying strong anomalies. The rare-earth kagome metal series, RMn6Sn6, provides a marvelous playground to study the electronic properties of kagome metals in the presence of variable magnetic order. Here, we report temperature-dependent reflectivity studies on two members of the RMn6Sn6 family, GdMn6Sn6 (in-plane ferrimagnet) and TbMn6Sn6 (out-of-plane ferrimagnet), in a broad energy range (50???18 000 cm???1, equivalent to 6.2 meV???2.23 eV) down to 10 K. At high temperatures, a phonon mode at ap-proximately 160 cm???1 is observed, which becomes screened out in TbMn6Sn6 below ???150 K as the localization peak linearly passes through the mode. In GdMn6Sn6, the disappearance of the phonon is accompanied by the onset of saturation of the peak position, suggesting an unusual interplay between the two features.

Automated summary

In this study, temperature-dependent reflectivity studies were conducted on two different magnetic order samples of rare-earth kagome metals. Peculiar optical spectra were observed, and changes in phonon mode at different temperatures were found. The results reveal an unusual interplay between two features.