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Optical conductivity of the Kondo insulator YbB12: Gap formation and low-energy excitations

H. Okamura, S. Kimura, H. Shinozaki, T. Nanba, F. Iga, N. Shimizu, and T. Takabatake
Phys. Rev. B 58, R7496(R) – Published 15 September 1998
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Abstract

Optical reflectivity experiments have been conducted on single crystals of the Kondo insulator YbB12 in order to obtain its optical conductivity, σ(ω). Upon cooling below 70 K, a strong suppression of σ(ω) is seen in the far-infrared region, indicating the opening of an energy gap of 25meV. This gap development is coincident with a rapid decrease in the magnetic susceptibility, which shows that the gap opening has significant influence on magnetic properties. A narrow, asymmetric peak is observed at 40meV in σ(ω), which is attributed to optical transitions between the Yb 4f-derived states across the gap. In addition, a broad peak is observed at 0.25eV. This peak is attributed to transitions between Yb 4f-derived states and the pd band, and is reminiscent of similar peaks previously observed for rare-earth hexaborides.

  • Received 12 May 1998

DOI:https://doi.org/10.1103/PhysRevB.58.R7496

©1998 American Physical Society

Authors & Affiliations

H. Okamura

  • Department of Physics, Kobe University, Kobe 657-8501, Japan

S. Kimura

  • Graduate School of Science and Technology, Kobe University, Kobe 657-8501, Japan
  • UVSOR Facility, Institute for Molecular Science, Myodaiji, Okazaki 444-8585, Japan

H. Shinozaki and T. Nanba

  • Graduate School of Science and Technology, Kobe University, Kobe 657-8501, Japan

F. Iga, N. Shimizu, and T. Takabatake

  • Graduate School of Advanced Science of Matter, Hiroshima University, Higashi-Hiroshima 739-8526, Japan

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Vol. 58, Iss. 12 — 15 September 1998

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