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| VOLUME 107 (2018) | ISSUE 2 | PAGE 108 |
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Collective infrared excitation in the cage-glass LuB12
B. P. Gorshunova,b, E. S. Zhukovaa, G. A. Komandinb, V. I. Torgashevc, A. V. Muratovd, Yu. A. Aleshchenkod, S. V. Demisheva,b, N. Yu. Shitsevalovae, V. B. Filipove, N. E. Sluchankoa,b
aMoscow Institute of Physics and Technology, 141700 Dolgoprudny, Russia bA.M. Prokhorov General Physics Institute, Russian Academy of Sciences, 119991 Moscow, Russia cFaculty of Physics, Southern Federal University, 344090 Rostov-on-Don, Russia dLebedev Physical Institute, Russian Academy of Sciences, 119991 Moscow, Russia eFrantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 03680 Kiev, Ukraine
Abstract
By measuring room temperature infrared (40-35000 cm-1) reflectivity of metallic LuB12 single crystals with different isotopic compositions (natB, 10B, 11B), we find that to model the spectrum we had to introduce, additionally to Drude free-carrier component, a broad excitation with unusually large dielectric contribution (  ) which is
characterized by a non-Lorentzian lineshape. It is suggested that the
origin of the excitation is connected with cooperative dynamics of
Jahn-Teller active B12 molecules producing quasi-local vibrations
(rattling modes) of caged lutetium ions. The coupling of the Lu3+
rattling motions with the charge carriers of conduction band is proposed
to be the reason of strongly damped character of the excitation.
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