Electron-Phonon Coupling and Symmetry-Breaking in Superconducting Oxide Interfaces Near Ferroelectric Quantum Criticality

Electron-Phonon Coupling and Symmetry-Breaking in Superconducting Oxide Interfaces Near Ferroelectric Quantum Criticality | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Physical Sciences - Article Electron-Phonon Coupling and Symmetry-Breaking in Superconducting Oxide Interfaces Near Ferroelectric Quantum Criticality Wu Zhou, Roger Guzman, Miguel Pruneda, Jean Paul Nery, Mingquan Xu, and 8 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6991826/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted You are reading this latest preprint version Abstract The observation of unconventional superconductivity in oxide quantum paraelectrics–materials exhibiting incipient ferroelectricity at low temperatures– raises fundamental questions about the role of ferroelectricity in the pairing mechanism. In oxide interfaces, such as LaAlO3/SrTiO3 (LAO/STO), quantum confinement and inversion symmetry breaking give rise to intriguing electronic phases, with charge doping driving the system toward a ferroelectric quantum critical point. However, direct experimental evidence of coupling between confined electrons and active phonon modes in a polar lattice has remained elusive. Here, we use momentum-selective vibrational electron energy loss spectroscopy (EELS) in scanning transmission electron microscopy (STEM) to simultaneously probe the atomic structure and phonon spectra across a series of LAO/STO interfaces with varying carrier concentrations and superconducting behavior. We find that the emergence of superconductivity correlates with interfacial lattice polarization and the appearance of new high-frequency, localized phonon modes. These modes, primarily involving in-plane and out-of-plane vibrations of equatorial and apical oxygen atoms in the TiO2 and SrO layers, respectively, are highly sensitive to carrier concentration. Our results provide compelling evidence for the coexistence of inversion symmetry breaking, superconductivity in the dilute limit, and strong electron-phonon coupling mediated by localized phonons, offering new insights into the microscopic pairing mechanism in quantum paraelectric systems. Physical sciences/Physics/Condensed-matter physics/Superconducting properties and materials Physical sciences/Physics/Condensed-matter physics/Surfaces, interfaces and thin films Full Text Additional Declarations There is NO Competing Interest. Supplementary Files LAOSTOvibEELSSupplementaryInformation.pdf Supplementary Information Cite Share Download PDF Status: Under Review Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6991826","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Physical Sciences - Article","associatedPublications":[],"authors":[{"id":485239948,"identity":"e216c9e9-0d59-4558-af3b-67ba44c9cc51","order_by":0,"name":"Wu Zhou","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAtklEQVRIiWNgGAWjYHACNiC2IV1LGulaDpOg3uBG+rMHH9vOJ/a3H3/A8KOGQd6csJaEdMOZbbcTZ5zJMWDsOcZguLOBgBazGwnHpHmBWjYw5DAw8DYwJBgcIKglsQ2o5VziBv7nDxj/EqclmQ2o5UDiBokEA2aibLE/84xNcsa5ZOMZN94YHJY5JmG4gZAWyfb0ZxIfyuxk+/vTHz58U2MjT9AWFABULEGK+lEwCkbBKBgFuAAA2rtAPKHP7PIAAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0002-6803-1095","institution":"University of Chinese Academy of Sciences","correspondingAuthor":true,"prefix":"","firstName":"Wu","middleName":"","lastName":"Zhou","suffix":""},{"id":485239949,"identity":"2de29c61-a2c9-43be-b0ab-0aa20181826b","order_by":1,"name":"Roger Guzman","email":"","orcid":"https://orcid.org/0000-0002-5580-0043","institution":"Institute of Materials Science of Barcelona","correspondingAuthor":false,"prefix":"","firstName":"Roger","middleName":"","lastName":"Guzman","suffix":""},{"id":485239950,"identity":"4b7a5584-1930-46da-beae-ede54508ddc1","order_by":2,"name":"Miguel Pruneda","email":"","orcid":"","institution":"Catalan Institute of Nanoscience and Nanotechnology","correspondingAuthor":false,"prefix":"","firstName":"Miguel","middleName":"","lastName":"Pruneda","suffix":""},{"id":485239951,"identity":"d65fd898-c00b-4e4e-9d47-818c30d64d4c","order_by":3,"name":"Jean Paul Nery","email":"","orcid":"","institution":"Institute of Materials Science of Barcelona (ICMAB-CSIC)","correspondingAuthor":false,"prefix":"","firstName":"Jean","middleName":"Paul","lastName":"Nery","suffix":""},{"id":485239952,"identity":"8291e49e-73a9-4321-b0d1-bfbdb1d54a69","order_by":4,"name":"Mingquan Xu","email":"","orcid":"","institution":"University of Chinese Academy of Sciences","correspondingAuthor":false,"prefix":"","firstName":"Mingquan","middleName":"","lastName":"Xu","suffix":""},{"id":485239953,"identity":"5bd485a0-7d1a-4340-9b1e-88a6634c7095","order_by":5,"name":"Aowen Li","email":"","orcid":"","institution":"University of Chinese Academy of Sciences","correspondingAuthor":false,"prefix":"","firstName":"Aowen","middleName":"","lastName":"Li","suffix":""},{"id":485239954,"identity":"96912ef1-c298-4379-b63c-1bee9da05cef","order_by":6,"name":"Nils Wittemeier","email":"","orcid":"","institution":"Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST","correspondingAuthor":false,"prefix":"","firstName":"Nils","middleName":"","lastName":"Wittemeier","suffix":""},{"id":485239955,"identity":"c40404d9-edb1-40e9-83d7-2c40d25281ee","order_by":7,"name":"Ang Li","email":"","orcid":"https://orcid.org/0009-0002-5967-0626","institution":"University of Chinese Academy of Sciences","correspondingAuthor":false,"prefix":"","firstName":"Ang","middleName":"","lastName":"Li","suffix":""},{"id":485239956,"identity":"0800aa4b-ee89-47ae-975b-cb09fa82f4b4","order_by":8,"name":"Gyanendra Singh","email":"","orcid":"","institution":"Institute of Materials Science of Barcelona (ICMAB-CSIC)","correspondingAuthor":false,"prefix":"","firstName":"Gyanendra","middleName":"","lastName":"Singh","suffix":""},{"id":485239957,"identity":"6ab4d0f6-65b4-4453-a220-b35421a6531e","order_by":9,"name":"Nicolas Bergeal","email":"","orcid":"https://orcid.org/0000-0002-9016-5305","institution":"ESPCI Paris - 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In oxide interfaces, such as LaAlO3/SrTiO3 (LAO/STO), quantum confinement and inversion symmetry breaking give rise to intriguing electronic phases, with charge doping driving the system toward a ferroelectric quantum critical point. However, direct experimental evidence of coupling between confined electrons and active phonon modes in a polar lattice has remained elusive. Here, we use momentum-selective vibrational electron energy loss spectroscopy (EELS) in scanning transmission electron microscopy (STEM) to simultaneously probe the atomic structure and phonon spectra across a series of LAO/STO interfaces with varying carrier concentrations and superconducting behavior. We find that the emergence of superconductivity correlates with interfacial lattice polarization and the appearance of new high-frequency, localized phonon modes. 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