{"id":117,"date":"2023-01-16T14:29:09","date_gmt":"2023-01-16T14:29:09","guid":{"rendered":"https:\/\/wp.icmm.csic.es\/seminars\/?p=117"},"modified":"2023-04-25T00:45:13","modified_gmt":"2023-04-25T00:45:13","slug":"julien-varignon-13-04-2023","status":"publish","type":"post","link":"https:\/\/wp.icmm.csic.es\/seminars\/2023\/01\/16\/julien-varignon-13-04-2023\/","title":{"rendered":"Julien Varignon (13\/04\/2023)"},"content":{"rendered":"<h2><img loading=\"lazy\" decoding=\"async\" class=\"size-medium wp-image-169 aligncenter\" src=\"https:\/\/wp.icmm.csic.es\/seminars\/wp-content\/uploads\/sites\/61\/2023\/01\/Julien-Varignon-300x300.jpeg\" alt=\"\" width=\"300\" height=\"300\" srcset=\"https:\/\/wp.icmm.csic.es\/seminars\/wp-content\/uploads\/sites\/61\/2023\/01\/Julien-Varignon-300x300.jpeg 300w, https:\/\/wp.icmm.csic.es\/seminars\/wp-content\/uploads\/sites\/61\/2023\/01\/Julien-Varignon-150x150.jpeg 150w, https:\/\/wp.icmm.csic.es\/seminars\/wp-content\/uploads\/sites\/61\/2023\/01\/Julien-Varignon.jpeg 512w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/h2>\n<h2 style=\"text-align: center\"><strong>Julien Varignon, <\/strong><\/h2>\n<h3 style=\"text-align: center\">Laboratoire CRISMAT, CNRS UMR 6508, ENSICAEN, Normandie Universit\u00e9, France<\/h3>\n<h2 style=\"text-align: center\">First-principles studies of oxide superconductors<\/h2>\n<h4 style=\"text-align: center\">When: 12:00-13:00 CET, April 13th (Thursday), 2023<\/h4>\n<h4 style=\"text-align: center\">Where: Seminar Room, ICMM-CSIC, Campus de Cantoblanco, Madrid<\/h4>\n<p>Along with the famous cuprates, ABiO3 (A=Ba, Sr) and BaSbO3 oxide perovskites as well as\u00a0nickel oxides, either as an infinite layer RNiO2 or Reduced Ruddlesden-Popper phase Rn+1NinO2(n+1)\u00a0(R=La, Pr or Nd), belong to the few oxide systems exhibiting superconductivity once appropriately\u00a0doped [Phys. Rev. B 37, 3745 (1988), Nature 390, 148 (1997), Nature 572, 624 (2019), Nat. Mater. 21,\u00a0160 (2021)]. They are thus alternative platforms for understanding the formation of bound electrons\u00a0at the core of superconductivity. However, these systems look rather different in their pristine form\u00a0(i) Ni+ cations exhibit a magnetic moment while Bi4+ or Sb4+cations do not, (ii) nickelates are prone to\u00a0correlation effects while the two other materials do not, (iii) RNiO2 compounds are metallic while\u00a0BaSbO3 and ABiO3 are insulators and (iv) nickelates and antimonates present a Mott-like regime while\u00a0ABiO3 materials possess a charge-transfer like behavior.\u00a0Although different at first glance, we reveal on the basis of Density Functional Theory (DFT)\u00a0calculations, involving all relevant degrees of freedom and an exchange-correlation functional\u00a0sufficiently amending self-interaction errors, that all these materials are prone to exhibit charge\u00a0orderings (CO) accompanied by bond disproportionation and insulating phases. Once doping drive the\u00a0materials in a metallic regime at the vicinity of a CO phase, the vibration associated with the bond\u00a0disproportionation is sufficient to explain the formation of Cooper pairs and to reproduce the\u00a0evolution of the critical temperature versus doping content observed experimentally for the different\u00a0compounds. Finally, strong hybridizations between the O-p states and the relevant cation states as\u00a0those appearing in bismuthates are shown to be a determining factor behind high temperature\u00a0superconductivity in oxides.<\/p>\n<p>YouTube link: <a href=\"https:\/\/www.youtube.com\/watch?v=Azs6rw0OlzE\">https:\/\/www.youtube.com\/watch?v=Azs6rw0OlzE<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Julien Varignon, Laboratoire CRISMAT, CNRS UMR 6508, ENSICAEN, Normandie Universit\u00e9, France First-principles studies of oxide superconductors When: 12:00-13:00 CET, April 13th (Thursday), 2023 Where: Seminar Room, ICMM-CSIC, Campus de Cantoblanco, Madrid Along with the famous cuprates, ABiO3 (A=Ba, Sr) and BaSbO3 oxide perovskites as well as\u00a0nickel oxides, either as an infinite layer RNiO2 or Reduced &hellip; <a href=\"https:\/\/wp.icmm.csic.es\/seminars\/2023\/01\/16\/julien-varignon-13-04-2023\/\" class=\"more-link\">Continue reading <span class=\"screen-reader-text\">Julien Varignon (13\/04\/2023)<\/span> <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n","protected":false},"author":103,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-117","post","type-post","status-publish","format-standard","hentry","category-sin-categoria"],"_links":{"self":[{"href":"https:\/\/wp.icmm.csic.es\/seminars\/wp-json\/wp\/v2\/posts\/117","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/wp.icmm.csic.es\/seminars\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/wp.icmm.csic.es\/seminars\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/wp.icmm.csic.es\/seminars\/wp-json\/wp\/v2\/users\/103"}],"replies":[{"embeddable":true,"href":"https:\/\/wp.icmm.csic.es\/seminars\/wp-json\/wp\/v2\/comments?post=117"}],"version-history":[{"count":6,"href":"https:\/\/wp.icmm.csic.es\/seminars\/wp-json\/wp\/v2\/posts\/117\/revisions"}],"predecessor-version":[{"id":192,"href":"https:\/\/wp.icmm.csic.es\/seminars\/wp-json\/wp\/v2\/posts\/117\/revisions\/192"}],"wp:attachment":[{"href":"https:\/\/wp.icmm.csic.es\/seminars\/wp-json\/wp\/v2\/media?parent=117"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wp.icmm.csic.es\/seminars\/wp-json\/wp\/v2\/categories?post=117"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wp.icmm.csic.es\/seminars\/wp-json\/wp\/v2\/tags?post=117"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}