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TT: Fachverband Tiefe Temperaturen
TT 17: Poster Session Correlated Electrons 1
TT 17.8: Poster
Montag, 16. März 2020, 15:00–19:00, P2/EG
Carrier relaxation dynamics in Kondo insulator YbB12 — •Amrit R Pokharel1, Steinn Y Agustsson1, Fumitoshi Iga2, Toshiro Takabatake2, Hidekazu Okamura3, and Jure Demsar1 — 1Johannes Gutenberg University Mainz, Germany — 2Graduate School of Advanced Sciences of Matter, Hiroshima University, Japan — 3Graduate School of Advanced Technology and Science, Tokushima University, Japan
We investigate the photoexcited quasiparticle relaxation dynamics in Kondo insulator YbB12 by means of time resolved all-optical pump-probe spectroscopy. In particular, we focus on temperature and excitation density dependent studies to address the temperature dependent changes in the low energy electron structure associated with the interplay/hybridization between the Yb 4f-levels and the conduction band electrons. At low temperatures, both the rise-time and recovery of the photoinduced reflectivity changes show dramatic temperature and excitation density dependence. The results are well accounted by the presence of the 15 meV indirect hybridization gap. While the static optical conductivity studies suggest the fully opening of gap around 20 K, our data implies its presence to much higher temperatures of the order of 150 K. Both, the dependence of build-up and its recovery on excitation density can be in detail accounted for by the phenomenological Rothwarf-Taylor model, describing the carrier relaxation across the narrow electronic gap, bottlenecked by the re-absorption of emitted phonons with energy larger than the gap.