{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"fc3ed542398c767b0cf7165ff5d729893ecc91fd6833deab374dfdd14fd17eee","created":"2026-10-03T07:17:59Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"e7f6d33af7d06a21659cd50ff9265b88cc24abb08afd57ad2ad3e1821a91bf93","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"identification","assisted_by":[],"external_id":"cm.cuprate-pseudogap.oscillation-pockets","kind":"well-posed","literature_status":"partially-resolved","n":"1","parents":[],"plain":"In strong magnetic fields, underdoped YBa2Cu3O6+x shows quantum oscillations, field-periodic wiggles in resistance that reveal a small closed pocket of electrons, whereas at zero field the Fermi surface is a single large hole-like contour; some order must cut the large surface into pieces.","posed_since":"2007","precise":"In YBa2Cu3O6+x ($p \\sim 0.08\\ \\text{to}\\ 0.15$) and HgBa2CuO4+d with superconductivity suppressed by $300\\ \\text{to}\\ 900\\,\\mathrm{kG}$, quantum oscillations show a dominant frequency $F \\sim 5.3\\,\\mathrm{MG}$ (about 2 percent of the Brillouin zone) and a negative Hall coefficient, indicating an electron pocket. Determine whether biaxial charge order with the measured $q_{\\mathrm{CDW}}$ alone reconstructs the Fermi surface into this electron pocket, and where the additional hole pockets required by Luttinger counting are, or why they are absent. An answer is a reconstruction model reproducing F, its splitting and c-axis warping, the Hall sign and the carrier count, together with detection or exclusion of the predicted extra pockets.","problem_ref":null,"references":"","settled_by":"Quantum-oscillation detection, or a bound on the amplitude, of the predicted hole pockets in the same field and doping range, plus angle-resolved oscillation data matching the proposed reconstruction.","status_note":"Reconstruction by charge order is the leading explanation of the electron pocket, but the hole pockets that such reconstructions predict have not been observed.","title":"What reconstructs the underdoped cuprate Fermi surface into small pockets","topic_ref":"0b1624cb419c381bddad004c2bf5315f0b67a5717967d1ceb30488890c34b90a"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"c2731729d4b609c42a63ef14bfdffea0ca9236413ca2b0e8ba77172a87e5e0cf","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"2936d0544f08bc6cfa5d0d4f6246db62ea7d8568120b94b876396a6c55c67af5","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"pyUGvA952V3O7rQnoHm6XNtvP3dp5z3i-lfwmT9CIIFjIVMZl8Q9zke0xb6qUPnEU3TG5y_2u-92vbpEPWQnCA"},"schema":"pubphys.envelope/1"},"record_hash":"c2731729d4b609c42a63ef14bfdffea0ca9236413ca2b0e8ba77172a87e5e0cf","leaf_index":931}