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Optical conductivity of Yb1xLuxB12: Energy gap and mid-infrared peak in diluted Kondo semiconductors

H. Okamura, M. Matsunami, T. Inaoka, T. Nanba, S. Kimura, F. Iga, S. Hiura, J. Klijn, and T. Takabatake
Phys. Rev. B 62, R13265(R) – Published 15 November 2000
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Abstract

We have measured the optical conductivity σ(ω) of Yb1xLuxB12 (0<~x<~1), where the system evolves from a Kondo semiconductor at x=0 to a nonmagnetic metal at x=1. For x=0, σ(ω) exhibits a clear energy gap with an onset at 20meV and a shoulder at 38 meV. As x increases, the gap is rapidly filled in from the bottom, while the shoulder remains at 40meV up to x=12. These results suggest that Lu substitution into YbB12 produces an in-gap band, but the characteristic energy for the gap remains unchanged in a wide range of x. Spectral evolutions of a characteristic mid-infrared peak, which results from Yb 4f-derived states near the Fermi level, suggest a strong coupling of Yb 4f electrons with conduction electrons.

  • Received 7 August 2000

DOI:https://doi.org/10.1103/PhysRevB.62.R13265

©2000 American Physical Society

Authors & Affiliations

H. Okamura, M. Matsunami, T. Inaoka, and T. Nanba

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

S. Kimura

  • Graduate School of Science and Technology, Kobe University, Kobe 657-8501, Japan
  • PRESTO, Japan Science and Technology Corporation, Kawaguchi 332-0012, Japan

F. Iga, S. Hiura, J. Klijn*, and T. Takabatake

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

  • *Permanent address: Van der Waals-Zeeman Laboratory, University of Amsterdam, 1018 XE Amsterdam, The Netherlands.

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Issue

Vol. 62, Iss. 20 — 15 November 2000

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