{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"6eaece98d3a67e982255397af9dfc7d891d72b410146632e35e207141b9092ee","created":"2026-10-03T07:17:59Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"7f490fca20dcf833582a381c0ae5b436d7a537c7d10bc0d441e5cbd356a7acce","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":"1","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 $3e17\\,\\mathrm{cm}^{-3}$, 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":null,"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":"1691597bf36b5c4ae6e8e76cab311c80818c254bf6df91fc1604cdef43bb8e76"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"c06b43052b569089ee2eb54d2f8ab4c94a606c214ded19648eea642882c7a4f6","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"b3bd82a19c40aea560670b8bf58972a2b7a4ed6844c7cb25a9724f35c30a527d","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"5D4BJyG9oL3G2m5e_7OkolB9J16RXkIKNxr0mtEveI82sbu-y8RiD_J_T8Zlt5D7xghwFwoCZxYAtKCwOzWVDw"},"schema":"pubphys.envelope/1"},"record_hash":"c06b43052b569089ee2eb54d2f8ab4c94a606c214ded19648eea642882c7a4f6","leaf_index":943}