{"id":3629,"date":"2026-02-25T09:55:37","date_gmt":"2026-02-25T08:55:37","guid":{"rendered":"https:\/\/www-preprod.cnrs-imn.fr\/event\/jeudis-de-la-chimie-du-solide-seminar-julien-varignon-crismat-caen\/"},"modified":"2026-04-17T12:27:00","modified_gmt":"2026-04-17T10:27:00","slug":"jeudis-de-la-chimie-du-solide-seminar-julien-varignon-crismat-caen","status":"publish","type":"tribe_events","link":"https:\/\/www.cnrs-imn.fr\/en\/event\/jeudis-de-la-chimie-du-solide-seminar-julien-varignon-crismat-caen\/","title":{"rendered":"Jeudis de la Chimie du Solide seminar &#8211; Julien Varignon (CRISMAT Caen)"},"content":{"rendered":"<p style=\"text-align: center;\"><strong>Charge and orbital orders drive superconductivity in complex oxides<\/strong><\/p>\n<p><img decoding=\"async\" class=\"alignnone size-full wp-image-5696 aligncenter\" src=\"https:\/\/www.cnrs-imn.fr\/wp-content\/uploads\/2026\/04\/Julien_Varignon.jpg\" alt=\"\" width=\"150\" height=\"150\" srcset=\"https:\/\/www.cnrs-imn.fr\/wp-content\/uploads\/2026\/04\/Julien_Varignon-66x66.jpg 66w, https:\/\/www.cnrs-imn.fr\/wp-content\/uploads\/2026\/04\/Julien_Varignon.jpg 150w\" sizes=\"(max-width: 150px) 100vw, 150px\" \/><\/p>\n<p style=\"text-align: center;\"><strong>Julien Varignon<\/strong><\/p>\n<p style=\"text-align: center;\"><a href=\"https:\/\/crismat.cnrs.fr\/\" target=\"_blank\" rel=\"noopener\">CRISMAT Laboratory, CNRS UMR 6508, ENSICAEN, Normandie University<\/a><\/p>\n<p align=\"justify\">Superconductivity, characterized by zero electrical resistance and expulsion of the magnetic field, remains limited by relatively modest critical temperatures Tc, reaching 135 K at best in cuprates at ambient pressure. In complex oxides, understanding the mechanisms by which Tc can be increased is a major challenge, particularly from the point of view of electronic and structural chemistry. <\/p>\n<p align=\"justify\">Oxides derived from Ruddlesden-Popper <sub>An+1BnO3n+1-type<\/sub> phases play a central role in this issue. In these systems, superconductivity frequently appears close to a transition between an insulating and a metallic phase. This transition is often associated with the disappearance of electronic orders such as charge orders (cationic dismutation) or orbitals, frequently linked to Jahn-Teller-type structural instabilities.  <\/p>\n<p align=\"justify\">In this seminar, I show, using first-principles simulations based on density functional theory (DFT), that superconductivity emerges systematically in the vicinity of these ordered phases. Even if these orders disappear in the metallic phase, their fluctuations persist and generate sufficient electron-phonon coupling to initiate superconductivity. <\/p>\n<p align=\"justify\">These results suggest that ordered insulating and superconducting phases share a common origin1<sup>,2<\/sup>. Finally, I demonstrate that structural distortions of <sub>O6<\/sub> octahedral lattices, such as rotations, can modulate this electron-phonon coupling. This opens the way to an oxide structural engineering strategy to optimize Tc.  <\/p>\n<p>______________________<\/p>\n<p>1. J. Varignon, M. Bibes, and A. Zunger, Nat. Comm. 10, 1658 (2019)<br \/>\n2. A. A. Carrasco-Alvarez, S. Petit, W. Prellier, M. Bibes, and J. Varignon, Nat.   Comm. 16, 1458 (2025)<\/p>\n<p>&nbsp;<\/p>\n<p><b><a class=\"moz-txt-link-freetext\" href=\"https:\/\/univ-nantes-fr.zoom.us\/j\/88146334543?pwd=8GL4UQasDKOmY9g5XmabSbPm0nDZx7.1\">https:\/\/univ-nantes-fr.zoom.us\/j\/88146334543?pwd=8GL4UQasDKOmY9g5XmabSbPm0nDZx7.1<\/a><\/b><b><br \/>\n<\/b><b>Meeting ID: 881 4633 4543<\/b><b><br \/>\n<\/b><b>Secret code: 468276<\/b><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Charge and orbital orders drive superconductivity in complex oxides Julien  [&#8230;]<\/p>\n","protected":false},"author":4,"featured_media":3631,"template":"","meta":{"_tribe_events_status":"","_tribe_events_status_reason":"","footnotes":""},"tags":[],"tribe_events_cat":[],"class_list":["post-3629","tribe_events","type-tribe_events","status-publish","has-post-thumbnail","hentry"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.4 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Jeudis de la Chimie du Solide seminar - Julien Varignon (CRISMAT Caen) - IMN<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.cnrs-imn.fr\/en\/event\/jeudis-de-la-chimie-du-solide-seminar-julien-varignon-crismat-caen\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Jeudis de la Chimie du Solide seminar - Julien Varignon (CRISMAT Caen) - IMN\" \/>\n<meta property=\"og:description\" content=\"Charge and orbital orders drive superconductivity in complex oxides Julien [...]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.cnrs-imn.fr\/en\/event\/jeudis-de-la-chimie-du-solide-seminar-julien-varignon-crismat-caen\/\" \/>\n<meta property=\"og:site_name\" content=\"IMN\" \/>\n<meta property=\"article:modified_time\" content=\"2026-04-17T10:27:00+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/www.cnrs-imn.fr\/wp-content\/uploads\/2026\/02\/Julien_Varignon-e1775722631458.jpg\" \/>\n\t<meta property=\"og:image:width\" content=\"174\" \/>\n\t<meta property=\"og:image:height\" content=\"200\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/jpeg\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data1\" content=\"1 minute\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\\\/\\\/www.cnrs-imn.fr\\\/en\\\/event\\\/jeudis-de-la-chimie-du-solide-seminar-julien-varignon-crismat-caen\\\/\",\"url\":\"https:\\\/\\\/www.cnrs-imn.fr\\\/en\\\/event\\\/jeudis-de-la-chimie-du-solide-seminar-julien-varignon-crismat-caen\\\/\",\"name\":\"Jeudis de la Chimie du Solide seminar - Julien Varignon (CRISMAT Caen) - IMN\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/www.cnrs-imn.fr\\\/#website\"},\"primaryImageOfPage\":{\"@id\":\"https:\\\/\\\/www.cnrs-imn.fr\\\/en\\\/event\\\/jeudis-de-la-chimie-du-solide-seminar-julien-varignon-crismat-caen\\\/#primaryimage\"},\"image\":{\"@id\":\"https:\\\/\\\/www.cnrs-imn.fr\\\/en\\\/event\\\/jeudis-de-la-chimie-du-solide-seminar-julien-varignon-crismat-caen\\\/#primaryimage\"},\"thumbnailUrl\":\"https:\\\/\\\/www.cnrs-imn.fr\\\/wp-content\\\/uploads\\\/2026\\\/02\\\/Julien_Varignon-e1775722631458.jpg\",\"datePublished\":\"2026-02-25T08:55:37+00:00\",\"dateModified\":\"2026-04-17T10:27:00+00:00\",\"breadcrumb\":{\"@id\":\"https:\\\/\\\/www.cnrs-imn.fr\\\/en\\\/event\\\/jeudis-de-la-chimie-du-solide-seminar-julien-varignon-crismat-caen\\\/#breadcrumb\"},\"inLanguage\":\"en-US\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\\\/\\\/www.cnrs-imn.fr\\\/en\\\/event\\\/jeudis-de-la-chimie-du-solide-seminar-julien-varignon-crismat-caen\\\/\"]}]},{\"@type\":\"ImageObject\",\"inLanguage\":\"en-US\",\"@id\":\"https:\\\/\\\/www.cnrs-imn.fr\\\/en\\\/event\\\/jeudis-de-la-chimie-du-solide-seminar-julien-varignon-crismat-caen\\\/#primaryimage\",\"url\":\"https:\\\/\\\/www.cnrs-imn.fr\\\/wp-content\\\/uploads\\\/2026\\\/02\\\/Julien_Varignon-e1775722631458.jpg\",\"contentUrl\":\"https:\\\/\\\/www.cnrs-imn.fr\\\/wp-content\\\/uploads\\\/2026\\\/02\\\/Julien_Varignon-e1775722631458.jpg\",\"width\":174,\"height\":200},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\\\/\\\/www.cnrs-imn.fr\\\/en\\\/event\\\/jeudis-de-la-chimie-du-solide-seminar-julien-varignon-crismat-caen\\\/#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Accueil\",\"item\":\"https:\\\/\\\/www.cnrs-imn.fr\\\/en\\\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"\u00c9v\u00e8nements\",\"item\":\"https:\\\/\\\/www.cnrs-imn.fr\\\/events\\\/\"},{\"@type\":\"ListItem\",\"position\":3,\"name\":\"Jeudis de la Chimie du Solide seminar &#8211; 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