Electronic Structure of B-2p State in AlB2 Single Crystal: Direct Observation ofpσand pπDensity of States

Abstract

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-2$p\sigma$ and $p\pi$ 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 $p\sigma$ orbitals of AlB${}_2$ near the Fermi energy, i.e., a pseudo-gap in $p\sigma$ state and a broad metallic state in $p\pi$ state are observed. The present result indirectly supports scenarios that the $p\sigma$ 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${}_2$.

LaTeX files and 4 eps figures, to be published in J. Phys. Soc. Jpn

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Cited by in corpus (1)

• Electronic Structure of B-2$p\sigma$ and $p\pi$ States in MgB${}_2$, AlB${}_2$ and ZrB${}_2$ Single Crystals