SKM 2021 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 9: Poster Session: Correlated Electrons
TT 9.7: Poster
Tuesday, September 28, 2021, 13:30–16:00, P
Robust hybridization gap in the Kondo insulator YbB12 probed by femtosecond optical spectroscopy — •Amrit raj Pokharel1, Steinn y. Agustsson1, Viktor v. Kabanov2, Fumitoshi Iga3, Toshiro Takabatake4, Hidekazu Okamura5, and Jure Demsar1 — 1JGU Mainz, Mainz, Germany — 2Jozef Stefan Institute, Ljubljana, Slovenia — 3Ibaraki University, Mito, Japan — 4Hiroshima University, Higashi-Hiroshima, Japan — 5Tokushima University, Tokushima, Japan
Carrier relaxation dynamics is susceptible to subtle changes in the low energy electronic structure. In heavy fermions the dynamics is shown to be governed by the low energy indirect gap, Eg, resulting from interplay/hybridization between localized moments and conduction band electrons. Here, carrier relaxation dynamics in a prototype Kondo insulator YbB12 is studied over large temperature range and over three orders of magnitude in excitation density. We utilize the intrinsic nonlinearity of dynamics to quantitatively determine microscopic parameters, such as electron-hole recombination rate. The extracted value reveals that hybridization is accompanied by a strong charge transfer from localized 4f levels. Furthermore, results suggest hybridization gap to be present up to temperatures of the order of Eg/kB ≈ 200 K, and is extremely robust against electronic excitation. Finally, the results imply further changes in the low energy electronic structure below 20 K, attributed to short-range antiferromagnetic correlations between the localized levels [1].
[1] A. R. Pokharel, et. al., Phys. Rev. B 103, 115134 (2021)