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<p>The discovery of superconductivity above 40 K in strained bilayer nickelates provides a tunable platform for exploring unconventional superconductivity under ambient pressure. However, the microscopic mechanisms driving this strain-induced state and how they contrast with high-pressure effects remain poorly understood. Here we show, using first-principles calculations across the rare-earth series RE<sub>3</sub>Ni<sub>2</sub>O<sub>7</sub>, that in-plane compressive strain systematically alters atomic structures and electronic hybridization. Wannier downfolding reveals that 2.5% compression enhances interlayer and in-plane orbital hoppings while significantly enlarging the crystal field splitting, which shifts the Ni <InlineEquation ID="IEq1"><EquationSource Format="TEX">\({d}_{{z}^{2}}\)</EquationSource><EquationSource Format="MATHML"><math><msub><mrow><mi>d</mi></mrow><mrow><msup><mrow><mi>z</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></msub></math></EquationSource></InlineEquation> bands entirely below the Fermi level. These findings elucidate the fundamental differences between strain-tuned and high-pressure electronic phases, offering critical guidance for optimizing superconducting properties in lanthanide-based thin films.</p>

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Structural and Electronic Evolution of Bilayer Nickelates Under Biaxial Strain

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年8月5日

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  • H. C. Regan B. Bhatta,
  • Xiaoliang Zhang,
  • Shuyi Li,
  • Yong Zhong,
  • Chunjing Jia

摘要

The discovery of superconductivity above 40 K in strained bilayer nickelates provides a tunable platform for exploring unconventional superconductivity under ambient pressure. However, the microscopic mechanisms driving this strain-induced state and how they contrast with high-pressure effects remain poorly understood. Here we show, using first-principles calculations across the rare-earth series RE3Ni2O7, that in-plane compressive strain systematically alters atomic structures and electronic hybridization. Wannier downfolding reveals that 2.5% compression enhances interlayer and in-plane orbital hoppings while significantly enlarging the crystal field splitting, which shifts the Ni \({d}_{{z}^{2}}\)dz2 bands entirely below the Fermi level. These findings elucidate the fundamental differences between strain-tuned and high-pressure electronic phases, offering critical guidance for optimizing superconducting properties in lanthanide-based thin films.