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<p>Several materials transition from an insulating to a superconducting state by reducing the strength of the electron-phonon coupling associated with charge and bond orderings provided that the coupling remains strong enough to produce Cooper pairs. While the Jahn-Teller effect is at the core of a strong electron-phonon coupling producing insulating states and orbital and bond orderings, its implication in superconductivity remains unobserved. Here, with parameter-free first-principles calculations, we reveal that superconductivity in A<sub>2</sub>RuO<sub>4</sub> (A = Sr, Ca) emerges due to an electron-phonon mechanism associated with the proximity of an orbital and bond-ordered phase. The model predicts critical temperatures <i>T</i><sub>c</sub> of 0.5–1.65 K in bulk Sr<sub>2</sub>RuO<sub>4</sub> and 63–73 K in pressured Ca<sub>2</sub>RuO<sub>4</sub>, in agreement with experiments. Our results suggest that phonons strongly coupled to electrons, such as those involved in charge disproportionation or Jahn-Teller effects and inducing band gaps in various oxides, could also serve as mediators of Cooper pairs in metallic phases.</p>

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Orbital-order as the driving mechanism for superconductivity in ruthenates

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年2月7日

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  • Álvaro Adrián Carrasco Álvarez,
  • Sébastien Petit,
  • Wilfrid Prellier,
  • Manuel Bibes,
  • Julien Varignon

摘要

Several materials transition from an insulating to a superconducting state by reducing the strength of the electron-phonon coupling associated with charge and bond orderings provided that the coupling remains strong enough to produce Cooper pairs. While the Jahn-Teller effect is at the core of a strong electron-phonon coupling producing insulating states and orbital and bond orderings, its implication in superconductivity remains unobserved. Here, with parameter-free first-principles calculations, we reveal that superconductivity in A2RuO4 (A = Sr, Ca) emerges due to an electron-phonon mechanism associated with the proximity of an orbital and bond-ordered phase. The model predicts critical temperatures Tc of 0.5–1.65 K in bulk Sr2RuO4 and 63–73 K in pressured Ca2RuO4, in agreement with experiments. Our results suggest that phonons strongly coupled to electrons, such as those involved in charge disproportionation or Jahn-Teller effects and inducing band gaps in various oxides, could also serve as mediators of Cooper pairs in metallic phases.