{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"371dd3f50b9b46a52bb8320641f440628b508e5e7a82601c04a78bb2842c31a1","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["c06b43052b569089ee2eb54d2f8ab4c94a606c214ded19648eea642882c7a4f6","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"2e231de4060ea7cef2722d46b53b18d683ae5c1a05a8f60d5a01d08d351645e8","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"mechanism","assisted_by":[],"external_id":"cm.dilute-superconductivity.bismuth-pairing","kind":"phenomenon","literature_status":"open","n":"2","parents":[],"plain":"Bismuth crystals, with roughly one mobile electron per hundred thousand atoms, become superconducting at about half a thousandth of a kelvin. Standard theory gives no reliable prediction at such low density with such light carriers.","posed_since":"2017","precise":"High-purity Bi single crystals superconduct at $T_{c} \\sim 0.53\\,\\mathrm{mK}$ (Prakash et al., Science 2017) with carrier density about $3 \\times 10^{17}\\,\\mathrm{cm}^{-3}$, Fermi energies of order $25\\,\\mathrm{meV}$ comparable to the Debye energy of order $10\\,\\mathrm{meV}$, so the Migdal adiabatic approximation fails. Compute $T_{c}$ from a controlled theory (Dirac-like bands with phonon coupling and screening) and determine the pairing symmetry. An answer is a mechanism giving $T_{c}$ within a factor of about 2 together with the predicted gap symmetry.","problem_ref":"c06b43052b569089ee2eb54d2f8ab4c94a606c214ded19648eea642882c7a4f6","references":"","settled_by":"A non-adiabatic pairing calculation reproducing $0.53\\,\\mathrm{mK}$ and the measured critical field, tested by the isotope or pressure dependence of $T_{c}$.","status_note":"","title":"How semimetallic bismuth superconducts at half a millikelvin","topic_ref":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"ba29a225a9e576e6a2e5f0026b8292603d1aa10ff22d8c3bd73ac526ea2c0fa4","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"ca1ef2317dded8f5d49114b4cee6c14484dbd8bfca634c011f7078f5eeb5c82a","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"LdRjviwktqox2inV8YYbLB1eRSr2zcVP6QxdqwiOnyaQpHDL_VPOmqIvRtcshJ9UXdS36eY7oCSa7uoYkdxwAQ"},"schema":"pubphys.envelope/1"},"record_hash":"ba29a225a9e576e6a2e5f0026b8292603d1aa10ff22d8c3bd73ac526ea2c0fa4","leaf_index":2740}