{"paper":{"title":"Ultrafast decoupling of quasiparticles and spin fluctuations in superconducting cuprates","license":"http://creativecommons.org/licenses/by/4.0/","headline":"Quasiparticles in cuprate superconductors decouple from spin fluctuations within 90 femtoseconds after a quench.","cross_cats":[],"primary_cat":"cond-mat.str-el","authors_text":"Christian Bernhard, Hideo Kishida, Hirotake Itoh, Jure Demsar, Kenji Yonemitsu, Ryo Kato, Shinichiro Iwai, Takahiko Sasaki, Tatsuya Amano, Terukazu Nishizaki, Yohei Kawakam, Yuto Nakamura, Yuto Taniguchi","submitted_at":"2026-05-14T01:10:07Z","abstract_excerpt":"Understanding how quasiparticles are generated following a rapid quench of superconductivity in high-Tc cuprates is a key unresolved problem in nonequilibrium superconductivity. Here we resolve these processes in optimally doped YBCO [YBa2Cu3Oy(y=6.94, Tc=92 K)] using broadband (0.16 -4.1 eV, ca. 100 fs) and nearly single-cycle (6 fs) transient reflectivity spectroscopy. We show that within a few femtosecond, enhanced electron-electron Umklapp scattering dominates, signaling a transient modulation of long-range Coulomb interactions on the eV scale. This regime is followed by a rapid suppressio"},"claims":{"count":4,"items":[{"kind":"strongest_claim","text":"We attribute this observation to an ultrafast decoupling of quasiparticles from the spin-fluctuation background, occurring on a 90 fs timescale set by the inverse optical gap.","source":"verdict.strongest_claim","status":"machine_extracted","claim_id":"C1","attestation":"unclaimed"},{"kind":"weakest_assumption","text":"The mid-infrared absorption feature is assumed to arise specifically from carriers dressed by spin fluctuations, so that its scattering-rate suppression directly signals decoupling rather than other relaxation channels or spectral-weight shifts.","source":"verdict.weakest_assumption","status":"machine_extracted","claim_id":"C2","attestation":"unclaimed"},{"kind":"one_line_summary","text":"Transient reflectivity measurements on YBCO reveal that quasiparticles decouple from spin fluctuations within 90 fs after a superconducting quench, set by the inverse optical gap.","source":"verdict.one_line_summary","status":"machine_extracted","claim_id":"C3","attestation":"unclaimed"},{"kind":"headline","text":"Quasiparticles in cuprate superconductors decouple from spin fluctuations within 90 femtoseconds after a quench.","source":"verdict.pith_extraction.headline","status":"machine_extracted","claim_id":"C4","attestation":"unclaimed"}],"snapshot_sha256":"22878b466816ba817b5598bfd1995ecf72981727df20d8d3654bfa2ffd543774"},"source":{"id":"2605.14238","kind":"arxiv","version":1},"verdict":{"id":"0409af10-59fb-40e7-8723-4ff4138cf043","model_set":{"reader":"grok-4.3"},"created_at":"2026-05-15T02:38:06.475696Z","strongest_claim":"We attribute this observation to an ultrafast decoupling of quasiparticles from the spin-fluctuation background, occurring on a 90 fs timescale set by the inverse optical gap.","one_line_summary":"Transient reflectivity measurements on YBCO reveal that quasiparticles decouple from spin fluctuations within 90 fs after a superconducting quench, set by the inverse optical gap.","pipeline_version":"pith-pipeline@v0.9.0","weakest_assumption":"The mid-infrared absorption feature is assumed to arise specifically from carriers dressed by spin fluctuations, so that its scattering-rate suppression directly signals decoupling rather than other relaxation channels or spectral-weight shifts.","pith_extraction_headline":"Quasiparticles in cuprate superconductors decouple from spin fluctuations within 90 femtoseconds after a quench."},"references":{"count":72,"sample":[{"doi":"","year":2016,"title":"C. Giannetti, M. Capone, D. Fausti, M. Fabrizio, F. Parmigiani, D. Mihailovic, Ultrafast optical spectroscopy of strongly correlated materials and high-temperature superconductors: a non-equilibrium a","work_id":"dec65099-4cb5-4806-b10e-5557755c13da","ref_index":1,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":2017,"title":"D. Basov, R. Averitt, D. Hsieh, Towards properties on demand in quantum materials. Nature. Mater. 16, 1077-1088 (2017)","work_id":"181bd2e2-2896-4040-91f6-7f21973706f7","ref_index":2,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":2018,"title":"A. Cavalleri, Photo-induced superconductivity. Comtemp. Phys. 59, 31-46 (2018)","work_id":"c028670d-8e56-42d0-959e-dc493a702f58","ref_index":3,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":2020,"title":"Demsar, Non-equilibrium phenomena in superconductors probed by femtosecond time-domain spectroscopy","work_id":"3af43914-a4f2-4265-b6ff-ea64a285993d","ref_index":4,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":2000,"title":"R. A. Kaindl, M. Woerner, T. Elsaesser, D. C. Smith, J. F. Ryan, G. A. Farnan, M. P. McCurry, D. G. Walmsley, Ultrafast Mid-Infrared Response of YBa2Cu3O7-δ. Science 287, 470-473 (2000)","work_id":"217c9665-2e47-4d43-802b-0f8a380f9b38","ref_index":5,"cited_arxiv_id":"","is_internal_anchor":false}],"resolved_work":72,"snapshot_sha256":"3d70bcd3e63050be5930887aa1df2829ae99add404e871a391f80c75af4a301d","internal_anchors":0},"formal_canon":{"evidence_count":2,"snapshot_sha256":"27963a3d6fbbe8468741a89cab90e99a7be57e63dc258ebd4a5117838e0ebfc7"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}