{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"4483594d46f3ffe825814e4e07e0ca96388a8e325f06696dd67c5d64f7e070e5","created":"2026-10-03T07:18:00Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"9238f25ee1af12b54e258202849295084a20ddcafb4be12c2365ddc261265b27","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"yes-no","assisted_by":[],"external_id":"cm.iron-based.s-pm-sign-change","kind":"well-posed","literature_status":"partially-resolved","n":"1","parents":[],"plain":"The leading theory says the pairing amplitude has opposite sign on different pockets of the Fermi surface ($s\\pm$ pairing); several experiments support it but a direct sign measurement is lacking.","posed_since":"2008","precise":"In bulk iron pnictides with both hole pockets at $\\Gamma$ and electron pockets at $M$ (for example Ba1-xKxFe2As2, LiFeAs), establish by a phase-sensitive probe whether the gap changes sign between them ($s\\pm$) or not ($s++$). An answer is a measurement in which the sign enters directly, such as a Josephson interferometer or phase-referenced quasiparticle interference with known impurity potentials.","problem_ref":null,"references":"","settled_by":"A phase-sensitive interference or Josephson experiment with an unambiguous sign signature reproduced in two materials.","status_note":"Neutron spin resonance and phase-referenced quasiparticle interference support $s\\pm$; some impurity-scattering results were argued to favor $s++$.","title":"Does the gap change sign between hole and electron pockets","topic_ref":"71fc7a5f7f45e0e897c1da37458bfa12479b8a0797fe32805a586a3c8fc44007"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"10792a105c208d2b2ed78b98e135cae2eaa7b263fcc6b163094b09ea866a72ca","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"d562368ea7ba22775b203f0438ead5a7d08657de7006ceb662176afb79727efa","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"wEy-tpJNem4ErTE5GR8p-waKweilhL1L4pV4reoo1B2lET4aD6H4dbUcy6KUUL7NL8TTrkIDRx8XSEd2PQoRDQ"},"schema":"pubphys.envelope/1"},"record_hash":"10792a105c208d2b2ed78b98e135cae2eaa7b263fcc6b163094b09ea866a72ca","leaf_index":1048}