Electronic Structure of B-2p State in AlB_2 Single Crystal : Direct Observation of pσ and pπ Density of States

概要

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X-ray emission (XES) and absorption (XAS) spectra near the B-K edge were measured on single-crystalline AlB_2 compound which is an isostructural diboride of superconducting MgB_2. The partial density of states (PDOS) of B-2pσ and pπ orbitals were derived from the polarization dependence of XES and XAS spectra. There are considerable amounts of PDOS near the Fermi energy in AlB_2 similarly to that in MgB_2,but there are almost no PDOS in pσ orbitals of AlB_2 near the Fermi energy, i.e., a pseudo-gap in pσ state and a broad metallic state in pπ state are observed. The present result indirectly supports scenarios that the pσ holes play an important role in the occurrence of superconductivity in MgB_2. The overall features of PDOS were found to be in good agreement with the result of band calculation of AlB_2,but a small discrepancy in the Fermi energy is observed, which is attributed to the Al vacancy in the compounds, i.e., the estimated concentration is Al_<0.93>B_2.
社団法人日本物理学会の論文
2002-02-15