{"paper":{"title":"Metallic crossover through the tilt-free transition in La$_3$Ni$_2$O$_7$ at high pressure and temperature","license":"http://creativecommons.org/licenses/by/4.0/","headline":"The tilt-free structural transition in La3Ni2O7 drives a two-order-of-magnitude increase in carrier density, crossing from bad metal to good metal.","cross_cats":[],"primary_cat":"cond-mat.supr-con","authors_text":"Bastien Michon, Beatrice D'Al\\`o, Bosen Wang, Elena Stellino, Ferenc Borondics, Francesco Capitani, Gergely N\\'emeth, Jianping Sun, Jinguang Cheng, Paolo Postorino, Yingpeng Yu","submitted_at":"2026-05-03T00:25:25Z","abstract_excerpt":"La$_3$Ni$_2$O$_7$, a bilayer nickelate with Ruddlesden-Popper structure, undergoes a pressure-induced structural transition from a tilted Amam phase to an untilted Fmmm (or I4/mmm) phase near 10-15 GPa, concomitant with the emergence of high-T$_c$ superconductivity ($T_c \\sim 80$ K). Despite intense interest, the phase boundaries and the impact of structural changes on the electronic properties remain unclear. Here, we combine high-pressure and high-temperature Raman and synchrotron-based infrared spectroscopies to map the structural and electronic evolutions. Raman measurements confirm the pr"},"claims":{"count":4,"items":[{"kind":"strongest_claim","text":"Infrared reflectivity measurements evidence a concomitant metallization, with a tremendous two-order-of-magnitude increase in carrier density, marking a crossover from a bad metal to a good metal.","source":"verdict.strongest_claim","status":"machine_extracted","claim_id":"C1","attestation":"unclaimed"},{"kind":"weakest_assumption","text":"That changes in infrared reflectivity can be interpreted as a direct two-order-of-magnitude carrier density increase without major contributions from scattering rate variations or other optical effects.","source":"verdict.weakest_assumption","status":"machine_extracted","claim_id":"C2","attestation":"unclaimed"},{"kind":"one_line_summary","text":"A metallic crossover from bad metal to good metal occurs at the tilt-free structural transition in La3Ni2O7 near 10-15 GPa, with carrier density rising by two orders of magnitude and similar signatures appearing above 544 K.","source":"verdict.one_line_summary","status":"machine_extracted","claim_id":"C3","attestation":"unclaimed"},{"kind":"headline","text":"The tilt-free structural transition in La3Ni2O7 drives a two-order-of-magnitude increase in carrier density, crossing from bad metal to good metal.","source":"verdict.pith_extraction.headline","status":"machine_extracted","claim_id":"C4","attestation":"unclaimed"}],"snapshot_sha256":"0b30cbe74a709229b556ecc7caeba0a39abb407a921fe746a8c6728947215d56"},"source":{"id":"2605.01651","kind":"arxiv","version":2},"verdict":{"id":"22d23a92-88ae-43ac-a6f3-9a6d2bcfd161","model_set":{"reader":"grok-4.3"},"created_at":"2026-05-09T17:09:55.008130Z","strongest_claim":"Infrared reflectivity measurements evidence a concomitant metallization, with a tremendous two-order-of-magnitude increase in carrier density, marking a crossover from a bad metal to a good metal.","one_line_summary":"A metallic crossover from bad metal to good metal occurs at the tilt-free structural transition in La3Ni2O7 near 10-15 GPa, with carrier density rising by two orders of magnitude and similar signatures appearing above 544 K.","pipeline_version":"pith-pipeline@v0.9.0","weakest_assumption":"That changes in infrared reflectivity can be interpreted as a direct two-order-of-magnitude carrier density increase without major contributions from scattering rate variations or other optical effects.","pith_extraction_headline":"The tilt-free structural transition in La3Ni2O7 drives a two-order-of-magnitude increase in carrier density, crossing from bad metal to good metal."},"integrity":{"clean":true,"summary":{"advisory":0,"critical":0,"by_detector":{},"informational":0},"endpoint":"/pith/2605.01651/integrity.json","findings":[],"available":true,"detectors_run":[{"name":"ai_meta_artifact","ran_at":"2026-05-20T17:38:47.620428Z","status":"completed","version":"1.0.0","findings_count":0},{"name":"doi_title_agreement","ran_at":"2026-05-20T05:01:23.609407Z","status":"completed","version":"1.0.0","findings_count":0},{"name":"doi_compliance","ran_at":"2026-05-19T17:06:49.414918Z","status":"completed","version":"1.0.0","findings_count":0}],"snapshot_sha256":"83e281317850a875537335874cac8b837fa2e6198c7bd58d9f76d5bf69240e8d"},"references":{"count":0,"sample":[],"resolved_work":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","internal_anchors":0},"formal_canon":{"evidence_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}