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<p>The origin of superconductivity in oxide interfaces and its relation to ferroelectricity remains an open question. At LaAlO<sub>3</sub>/SrTiO<sub>3</sub> interfaces, quantum confinement and inversion symmetry breaking create a two-dimensional electron gas near a ferroelectric quantum critical point, yet direct evidence linking phonon dynamics to electron pairing has been lacking. Here we directly probe lattice vibrations and atomic structure at LaAlO<sub>3</sub>/SrTiO<sub>3</sub> interfaces across the superconducting phase diagram using vibrational spectroscopy with momentum selectivity in a scanning transmission electron microscope. We find that superconductivity across the doping series correlates with inversion symmetry breaking and the appearance of high-frequency localized phonons. These tunable, polar vibrations—confined near the interface—exhibit strong electron–phonon coupling and evolve systematically with carrier density. Our findings establish a link between lattice instability, superconductivity and strong electron–phonon coupling mediated by tunable localized phonons, providing new insights into possible microscopic pairing pathways in quantum paraelectric systems.</p>

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Electron–phonon coupling and symmetry breaking in superconducting oxide interfaces near ferroelectric quantum criticality

  • 期刊论文

  • 发表日期：

    2026年6月30日

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  • Roger Guzman,
  • Miguel Pruneda,
  • Jean Paul Nery,
  • Mingquan Xu,
  • Aowen Li,
  • Nils Wittemeier,
  • Ang Li,
  • Gyanendra Singh,
  • Nicolas Bergeal,
  • Alexei Kalaboukhov,
  • Gervasi Herranz,
  • Jaume Gazquez,
  • Wu Zhou

摘要

The origin of superconductivity in oxide interfaces and its relation to ferroelectricity remains an open question. At LaAlO3/SrTiO3 interfaces, quantum confinement and inversion symmetry breaking create a two-dimensional electron gas near a ferroelectric quantum critical point, yet direct evidence linking phonon dynamics to electron pairing has been lacking. Here we directly probe lattice vibrations and atomic structure at LaAlO3/SrTiO3 interfaces across the superconducting phase diagram using vibrational spectroscopy with momentum selectivity in a scanning transmission electron microscope. We find that superconductivity across the doping series correlates with inversion symmetry breaking and the appearance of high-frequency localized phonons. These tunable, polar vibrations—confined near the interface—exhibit strong electron–phonon coupling and evolve systematically with carrier density. Our findings establish a link between lattice instability, superconductivity and strong electron–phonon coupling mediated by tunable localized phonons, providing new insights into possible microscopic pairing pathways in quantum paraelectric systems.