{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"957e8670fe358cc0e82d1742b69260e9a75f4209505e5812d4b8e559015e317a","created":"2026-10-03T07:18:00Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"6b056eb6dd7dd00118cc68321cfa630232335631abcb9013c39915a173fda422","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"identification","assisted_by":[],"external_id":"cm.nickelates.bulk-sc-polymorph","kind":"well-posed","literature_status":"partially-resolved","n":"1","parents":[],"plain":"Early pressure experiments found only a small superconducting volume, and La3Ni2O7 crystals contain two stacking patterns of nickel-oxide layers, so which structure superconducts in bulk was unclear.","posed_since":"2023","precise":"Determine which structural polymorph of La3Ni2O7 at high pressure (bilayer 2222 or alternating monolayer-trilayer 1313) carries the $\\sim 80\\,\\mathrm{K}$ superconductivity, and whether the superconducting volume fraction in phase-pure stoichiometric crystals is bulk. An answer combines diffraction under pressure with ac susceptibility volume fractions on the same phase-pure samples.","problem_ref":null,"references":"","settled_by":"Shielding-fraction measurements near 100 percent on phase-pure samples of each polymorph with simultaneous structural determination.","status_note":"Bulk superconductivity was reported in La2PrNi2O7 under pressure (2024) and in pressurized bilayer nickelate crystals up to about $96\\,\\mathrm{K}$ (2025), and superconductivity was also reported in the 1313 polymorph (2025).","title":"Which La3Ni2O7 polymorph carries bulk superconductivity under pressure","topic_ref":"1addbb7974855cb74617281e1add5f43c41622b4152f1b5d331c3da3827c5d62"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"b3a2b4f7e2cc646c0fa3d74d645e3e321a0a0842e50635e3da3e2c2840f55d81","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"cdb91c3f9c1b246d91eef2b0fc2d11e672f4e33844e2e313f9fd7dff5197528d","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"efg82Hs-vQr1BQfilbLyq-nGaXQ_reCNty5nS4jmecHlg_Jj-LOoGAaM8HR8o5etCX7z8OO22XS6KfhNuyLyBg"},"schema":"pubphys.envelope/1"},"record_hash":"b3a2b4f7e2cc646c0fa3d74d645e3e321a0a0842e50635e3da3e2c2840f55d81","leaf_index":1109}