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

Jin Nakamura·Masamitsu Watanabe·Tamio Oguchi·Sin-ya Nasubida·Eiki Kabasawa·Nobuyoshi Yamada·Kazuhiko Kuroki·Hisashi Yamazaki·Shik Shin·Yuji Umeda·Shin Minakawa·Noriaki Kimura·Haruyoshi Aoki
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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$pσ$ 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$_2$.

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Jin Nakamura, Masamitsu Watanabe, Tamio Oguchi, Sin-ya Nasubida, Eiki Kabasawa, Nobuyoshi Yamada, Kazuhiko Kuroki, Hisashi Yamazaki, Shik Shin, Yuji Umeda, Shin Minakawa, Noriaki Kimura, Haruyoshi Aoki. 2001-12-21. Electronic Structure of B-2p State in AlB2 Single Crystal: Direct Observation ofpσand pπDensity of States. https://doi.org/10.1143/jpsj.71.408

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