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Moiré-resonant surface state in ultrathin RuO2(110)

Philipp Keßler1,2, Andreas Feuerpfeil2,3, Armando Consiglio2,3,4, Hendrik Hohmann2,3, Ronny Thomale2,3, Jonas Erhardt1,2, Bing Liu1,2, Vedran Jovic5,6, Ralph Claessen1,2 et al.

Patrick Härtl1,2, Matteo Dürrnagel2,3,7, and Simon Moser8,1,2,*

  • *Contact author: simon.moser@ruhr-uni-bochum.de
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Phys. Rev. Research 8, 033058 – Published 13 July, 2026

DOI: https://doi.org/10.1103/cvqr-4wkd

Abstract

RuO2 has emerged as a prototypical candidate for altermagnetism. In the face of daunting evidence for magnetic order in the bulk, the focus naturally shifted to surfaces and ultrathin films, where Coulomb interactions are dimensionally quenched and electron correlations strongly enhanced. Here, we examine atomically ordered, ultrathin RuO2(110) grown on Ru(0001) using a combination of scanning tunneling microscopy (STM), density functional theory, and density matrix renormalization group methods. We observe a nonmagnetic charge order that is imprinted by the incommensurate moiré stacking with the substrate and enhanced by the electronic Fermi-surface scattering within the flat-band surface state. We further identify a nonmagnetic, metastable c(2×2) surface reconstruction that arises from surface phonon softening and can be toggled reversibly via STM tip manipulation. Spin-polarized STM measurements, however, reveal no evidence of magnetic order on the RuO2(110) surface. Our findings of a nonmagnetic charge modulation position ultrathin RuO2(110) as an intriguing platform for exploring moiré-assisted electronic orders.

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Phys. Rev. Research 8, 033058– Published 13 July, 2026
  • Received 24 July 2025
  • Revised 10 February 2026
  • Accepted 10 June 2026
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