Strain-enhanced superconductivity in RuO2 thin films: Joint experimental and theoretical studies
Abstract
We investigate the superconducting properties of RuO2 films grown on TiO2 substrates by combining film fabrication and transport measurement with \textit{ab initio} calculation. Experimentally, we grow several RuO2 (110) thin films on TiO2 (110) substrates and observe superconductivity with critical temperature (Tc) of ∼2.0 K in 20-nm and 30-nm RuO2 (110) thin films. Theoretically, we study the superconductivity in both RuO2 (110) and RuO2 (100) epitaxial films within McMillan formalism of isotropic Migdal-Eliashberg theory. Among the salient results, the calculated phonon dispersion relations of all the considered RuO2 films show that the epitaxial films are dynamically stable. Importantly, our \textit{ab initio} calculations reveal that independent of the film orientation, the [001] compressive strain ε[001] pushes the flat Ru dz2-dominant bands towards the Fermi level (EF), and significantly soften the out-of-plane acoustic phonon mode near the R point in the Brillouin zone, which substantially enhances the electron-phonon coupling (EPC) strength λ and hence the calculated Tc in the RuO2 films. Remarkably, the amount of the phonon softening and the enhanced Tc increase almost linearly with the increasing ε[001]. The calculated Tc for the films with thickness of ≥ 20 nm agree well with the experimental Tc. These findings demonstrate that among other things, lattice mismatch strain provides an effective route for tuning phonon-mediated superconductivity in RuO2 and other thin films.
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BibTeX
@misc{din2026strainenhanced,
title = {{Strain-enhanced superconductivity in RuO$_2$ thin films: Joint experimental and theoretical studies}},
author = {Moeen ud din and Tsun-Sung Kuo and Yun-Chen Liao and Akhilesh Kr. Singh and Uddipta Kar and Wei-Li Lee and Guang-Yu Guo},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.21163},
eprint = {2610.21163},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.21163},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Strain-enhanced superconductivity in RuO_2 thin films: Joint experimental and theoretical studies
AU - Moeen ud din
AU - Tsun-Sung Kuo
AU - Yun-Chen Liao
AU - Akhilesh Kr. Singh
AU - Uddipta Kar
AU - Wei-Li Lee
AU - Guang-Yu Guo
PY - 2026
DA - 2026/10/15
PB - arXiv
DO - 10.48550/arxiv.2610.21163
UR - https://arxiv.org/abs/2610.21163
AB - We investigate the superconducting properties of RuO_2 films grown on TiO_2 substrates by combining film fabrication and transport measurement with \textit{ab initio} calculation. Experimentally, we grow several RuO_2 (110) thin films on TiO_2 (110) substrates and observe superconductivity with critical temperature (T_c) of ∼2.0 K in 20-nm and 30-nm RuO_2 (110) thin films. Theoretically, we study the superconductivity in both RuO_2 (110) and RuO_2 (100) epitaxial films within McMillan formalism of isotropic Migdal-Eliashberg theory. Among the salient results, the calculated phonon dispersion relations of all the considered RuO_2 films show that the epitaxial films are dynamically stable. Importantly, our \textit{ab initio} calculations reveal that independent of the film orientation, the [001] compressive strain ε_[001] pushes the flat Ru d_z^2-dominant bands towards the Fermi level (E_F), and significantly soften the out-of-plane acoustic phonon mode near the R point in the Brillouin zone, which substantially enhances the electron-phonon coupling (EPC) strength λ and hence the calculated T_c in the RuO_2 films. Remarkably, the amount of the phonon softening and the enhanced T_c increase almost linearly with the increasing ε_[001]. The calculated T_c for the films with thickness of ≥ 20 nm agree well with the experimental T_c. These findings demonstrate that among other things, lattice mismatch strain provides an effective route for tuning phonon-mediated superconductivity in RuO_2 and other thin films.
ER -