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arXiv · 1807.01426

Observation of a Dirac nodal line in AlB2

Daichi Takane·Seigo Souma·Kosuke Nakayama·Takechika Nakamura·Hikaru Oinuma·Kentaro Hori·Kouji Horiba·Hiroshi Kumigashira·Noriaki Kimura·Takashi Takahashi·Takafumi Sato
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Abstract

We have performed angle-resolved photoemission spectroscopy of AlB2 which is isostructural to high-temperature superconductor MgB2. Using soft-x-ray photons, we accurately determined the three-dimensional bulk band structure and found a highly anisotropic Dirac-cone band at the K point in the bulk hexagonal Brillouin zone. This band disperses downward on approaching the H point while keeping its degeneracy at the Dirac point, producing a characteristic Dirac nodal line along the KH line. We also found that the band structure of AlB2 is regarded as a heavily electron-doped version of MgB2 and is therefore well suited for fully visualizing the predicted Dirac nodal line. The present results suggest that (Al,Mg)B2 system is a promising platform for studying the interplay among Dirac nodal line, carrier doping, and possible topological superconducting properties.

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Daichi Takane, Seigo Souma, Kosuke Nakayama, Takechika Nakamura, Hikaru Oinuma, Kentaro Hori, Kouji Horiba, Hiroshi Kumigashira, Noriaki Kimura, Takashi Takahashi, Takafumi Sato. 2018-07-18. Observation of a Dirac nodal line in AlB2. https://doi.org/10.1103/physrevb.98.041105

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