{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"96c5f3830532de9036673e410485df35bd4ca9008edf7416577ac3b3a19aba90","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":["ai:gpt-5.5"],"kind":"seed"},"parents":["8afab1f4db9b49b9de595aa668ea1b6326119c4e988e49ede6d80c790de4aa8c","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"1842f2a6b8fdb5b1b6e5e797706ea887fe6fca796e98a5ff7d4f0c558bdf6388","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"classification","assisted_by":["ai:gpt-5.5"],"external_id":"cm.cuprate-pseudogap.pstar-critical-point","kind":"well-posed","literature_status":"contested","n":"2","parents":[],"plain":"Near 19 percent hole doping the pseudogap vanishes, and there the electronic heat capacity peaks and resistance becomes linear in temperature, signs of a phase transition at zero temperature.","posed_since":"","precise":"With superconductivity suppressed by fields of several hundred kG, determine whether the endpoint $p*$ (0.19 to 0.23 depending on family) is a quantum critical point with an order parameter ($C/T \\sim \\log(1/T)$, Hall number change from $p\\ \\text{to}\\ 1+p$) or a change of Fermi-surface topology without broken symmetry. An answer identifies the transition type and, if one exists, the order parameter whose fluctuations give the log divergence.","problem_ref":"8afab1f4db9b49b9de595aa668ea1b6326119c4e988e49ede6d80c790de4aa8c","references":"","settled_by":"Detection of the order parameter (or proof of its absence) by a symmetry-sensitive probe in the same high-field regime where C/T diverges.","status_note":"High-field specific heat (2019) found $C/T \\sim \\log(1/T)$ at $p*$ in Nd- and Eu-substituted La2-xSrxCuO4, but the associated order parameter is unidentified.","title":"Is the pseudogap endpoint $p*$ a quantum critical point?","topic_ref":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"ac887e02336f525544c7a4dbb00a087b52d50df9c2552d72e1d08f1bb60292f1","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"df7327cc6e392a5e43d4d4dc911d3c85f48065b497c903033963da85244a1a4f","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"sBm7B4D1TBSUVYvfFRnbb5Eff1J2Vh7KYItpDcpmeCHuJQsGa_PyM8B55kFdyskw-FT69fEJEsDXunZJncXoAA"},"schema":"pubphys.envelope/1"},"record_hash":"ac887e02336f525544c7a4dbb00a087b52d50df9c2552d72e1d08f1bb60292f1","leaf_index":2726}