Presentation Information
[3C12【女子大学院生優秀賞2024】]Synthesis of novel free-standing atomic layers and research into line-node semimetals
*Xiaoni Zhang1, Yuki Tsujikawa1, Masashige Miyamoto1, Mei Yuan2, Kazuki Yamaguchi1, Masafumi Horio1, Kenichi Ozawa3, Kunio Yubuta4, Takahiro Kondo2, Iwao Matsuda1 (1. The Institute for Solid State Physics, University of Tokyo, 2. Institute of Pure and Applied Sciences, University of Tsukuba, 3. Institute of Materials Structure Science, KEK, 4. Institute for Aqua Regeneration, Shinshu University)
Boron, as an electron-deficient element, is a promising platform for realizing two-dimensional Dirac materials. Hydrogen boride (HB) with five- and seven-membered boron rings (5,7-HB) was recently synthesized from RMB-type metallic borides, forming a non-symmorphic Pbam lattice known to host Dirac nodal loops. Topological classifications predict 5,7-HB as a Dirac nodal semimetal, supported by X-ray spectroscopy confirming its gapless nature, unlike the semiconducting parent YCrB4. In this study, free-standing 5,7-HB sheets were synthesized from YCrB4 via a controlled ion-exchange reaction. By tuning synthesis conditions, three electronic phases were achieved: semimetallic sheets with a clear Fermi edge, porous sheets with reduced density of states near the Fermi level, and oxygen-modified sheets showing insulating behavior. These results reveal that the electronic properties of 5,7-HB can be systematically tailored through chemical processing, offering a new platform for nanoscale electronic and sensing applications.