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Off-stoichiometric surface reconstruction in the altermagnetic candidate RuO2(100)/Ru(101¯0)

Sungsoo Hahn1,*,†, Minkyu Park1,*, Yeonghoon Lee1, Changsoo Kim1, Jahyun Koo1, Minhyuk Choi1, Seungwoo Song1, S. H. Rhim2, Changyoung Kim3 et al.

Chanyong Hwang1,‡

  • *These authors contributed equally to this work.
  • †Contact author: shahn@kriss.re.kr
  • ‡Contact author: cyhwang@kriss.re.kr
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Phys. Rev. B 111, 214431 – Published 23 June, 2025

DOI: https://doi.org/10.1103/zhm5-k3wr

Abstract

Recently, RuO2 has gained significant attention as a promising altermagnetic candidate. However, the presence of magnetism in RuO2 has been a topic of ongoing debate, with stoichiometry identified as a key factor by Smolyanyuk et al. [Phys. Rev. B 109, 134424 (2024)]. To explore the stoichiometric effects in RuO2, we oxidized pure single-element Ru at several temperatures. The band structure modulation near Fermi level by stoichiometric variation was clearly observed by in situ angle-resolved photoemission spectroscopy. First-principles calculations revealed that this evolution was relevant to surface reconstruction induced by excessive O rather than altermagnetism. Additionally, our results indicate that the experimentally measured band structure of RuO2(100)/Ru(101¯0) aligns well with the nonmagnetic band calculations. Our findings not only provide a clue to resolve the current experimental discrepancy but also support the nonmagnetic ground state of RuO2 films grown on Ru metal.

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Phys. Rev. B 111, 214431– Published 23 June, 2025
  • Received 26 November 2024
  • Revised 7 April 2025
  • Accepted 19 May 2025
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