{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"fd4dc0cbc09b5d70a923147a60aebe24e3f238798981bccfd46da364ea2a51d4","created":"2026-10-03T07:18:01Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"e2bf1c993832326f86d1bdc934472346b708612234ecfdd94fafa3bbcb4d23cc","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"classification","assisted_by":[],"external_id":"cm.sit-anomalous-metal.critical-universality","kind":"well-posed","literature_status":"contested","n":"1","parents":[],"plain":"Theory predicted that at the switch between superconductor and insulator the film resistance takes a universal value set by Planck constant and the electron charge, with simple scaling laws. Experiments find different values and exponents in different films.","posed_since":"1990","precise":"The dirty-boson theory (Fisher 1990) predicts a universal critical sheet resistance $R_{c} = h/(4e^{2})$ and universal $z\\nu$ at the B- or disorder-tuned transition. Measured $R_{c}$ varies by a factor of several and $z\\nu$ ranges from $\\sim 0.6$ to above 2; Ga films show a divergent effective $z\\nu$ characteristic of a quantum Griffiths singularity (Xing et al. 2015). Classify the universality classes of the 2D transition with $1/r$ Coulomb interaction and quenched disorder, and determine whether $R_{c}$ and $z\\nu$ are universal within each class.","problem_ref":null,"references":"","settled_by":"Scaling analyses at $T$ far below the crossover scale in several material classes, with sample-to-sample comparison of $R_{c}$ and $z\\nu$, matched to a theory assigning each to a class.","status_note":"A discontinuous (first-order) disorder-driven transition was reported in amorphous InOx films (Charpentier et al., Nature Physics 21, 104, 2025), which would place at least some films outside any continuous universality class.","title":"Are critical resistance and exponents at the 2D superconductor-insulator transition universal?","topic_ref":"4ea1b2157b1b787fb021cb15b1d29d6f209084de7dc217220a6bd4b6bab225a2"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"7c9e615798a890dd8993d86e287ecf7fd57701ff19c9c2c0ca278364747c568e","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"04217cefcae0358020704176ad23fc1985cd010dd2f059200e6584eae65c9e32","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"XIwRVK2318trHXUt8XzWmffoY2SsIGgVzO_q4uXGXsY5ombcaxV0CVd6zxtDmdZIAjGGDbVxeY1UJy6Ht9XLCQ"},"schema":"pubphys.envelope/1"},"record_hash":"7c9e615798a890dd8993d86e287ecf7fd57701ff19c9c2c0ca278364747c568e","leaf_index":1158}