Optical spectroscopy study of the electronic structure of Eu 1-xCa xB 6

Jung Ho Kim, Youngwoo Lee, C. C. Homes, Jong Soo Rhyee, B. K. Cho, S. J. Oh, E. J. Choi

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The room temperature optical conductivity σ 1(ω) of Eu 1-xCa xB 6 has been obtained from reflectivity and ellipsometry measurements for a series of compositions, 0 ≤x≤1. The interband part of σ 1(ω) shifts continuously to higher frequency as Ca content x increases. Also the intraband spectral weight of σ 1(ω) decreases rapidly and essentially vanishes for x≥x c=0.35. These results show that the valence band and the conduction band of Eu 1-xCa xB 6 move away from each other such that their band overlap decreases with increasing Ca substitution. As a result, the electronic state evolves from the semimetallic structure of EuB 6 to the insulating CaB 6 where the two bands are separated to open a finite gap (≃0.25 eV) at the X point of the Brillouin zone.

Original languageEnglish
Article number075105
JournalPhysical Review B - Condensed Matter and Materials Physics
Issue number7
StatePublished - Feb 2005


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