{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"8f6e15c86758d04536d0f38d7bbd1396d571272ccba787120ffae922c45a53c7","created":"2026-10-03T07:17:59Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011","946651e45560029973e85184727aeb29e0c77ad6e6c7e6779b82d81a1358b32c"],"salt":"5557d601173ab615b091e09c6f6a97096fa73ee95fa846b14e1a93f80c7d096a","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"classification","assisted_by":[],"external_id":"cm.cuprate-pseudogap.pstar-critical-point","kind":"well-posed","literature_status":"contested","n":"1","parents":[{"note":"","parent_revision":"946651e45560029973e85184727aeb29e0c77ad6e6c7e6779b82d81a1358b32c","relation":"special_case"}],"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 ($C/T \\sim \\operatorname{log}(1/T)$, 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":null,"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":"0b1624cb419c381bddad004c2bf5315f0b67a5717967d1ceb30488890c34b90a"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"8afab1f4db9b49b9de595aa668ea1b6326119c4e988e49ede6d80c790de4aa8c","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"b59b633e6a5252665e31f767cb9613b7aa0b302f631c419deb46db8a485bc47d","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"hU692RtSjjV7k2eYi7pU5hc1m_gMgie64x56xbylzDGJXWE3rF040CaROcgrRUtcvtal9fo2sxpc5xJ900KRCQ"},"schema":"pubphys.envelope/1"},"record_hash":"8afab1f4db9b49b9de595aa668ea1b6326119c4e988e49ede6d80c790de4aa8c","leaf_index":932}