XPSによるMgB2内電子状態の温度依存性の研究

概要

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We have measured, at room temperature and 16K, the Bls, Mg2s, and Mg2p XPS spectra, and the MgKLLAuger spectra of MgB2, which has the highest TC(39K) except for the high-Tc superconducting cuprates. For comparison, we have also measured the Cls XPS spectra of graphite, a C atom of which is in the same isoelectronic sequence as a B atom of MgB2 is. As for the peak positions between the XPS spectra taken at room temperature and 16K, the difference is not observed in the spectra derived from Mg core-levels. As a result, it might be thought that 〓q = 0, where 〓q is an amount of the change of the valence charge in an atom. This means that the valence charge of the Mg atom hardly change, and agrees with other experimental results. On the other hand, the Blj spectra might reveal that〓q〓 0, and this is contrary to the case of Cls spectra. This implies that the amount of the valence charge of a B atom almost remains or increases with temperature decreasing. The result seems not to agree with other experimental results in which the valence electrons tend to be localized in a honeycomb plain constructed from B atoms in the superconducting phase.
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