{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"3553eda3371202015d0aed29a5fad7d336a8d597579ee66ca67d0922fd9581e7","created":"2026-10-03T07:17:59Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"ebed9ec673b3501811ea7af043f999a22dfeef14036335fa61863b5f5ee3b4c5","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"identification","assisted_by":[],"external_id":"cm.heavy-fermions.uru2si2-hidden-order","kind":"well-posed","literature_status":"contested","n":"1","parents":[],"plain":"Below 17.5 K, URu2Si2 enters an ordered phase that releases a large amount of entropy, yet nearly forty years of experiments have not identified what orders.","posed_since":"1985","precise":"Identify the order parameter of the phase below $T_{\\mathrm{HO}} = 17.5\\ \\mathrm{K}$ in URu2Si2, which has no ordered magnetic moment of matching size and doubles the unit cell along c (wavevector $(0,0,1)$). Candidates include higher-rank multipoles (hexadecapole, dotriacontapole), hastatic order and chirality density waves. An answer gives the symmetry (irreducible representation) and microscopic character, confirmed by a probe that couples directly to it (resonant x-ray scattering, Raman, NMR).","problem_ref":null,"references":"","settled_by":"A direct detection of the proposed order parameter whose temperature dependence follows $T_{\\mathrm{HO}}$ and vanishes under pressure-induced antiferromagnetism.","status_note":"Raman data (2015) show an A_2g mode suggesting chirality-density-wave order, while reports of in-plane fourfold symmetry breaking disagree between probes.","title":"What is the order parameter of hidden order in URu2Si2","topic_ref":"348f0bf7a34a765b71c6ebd8ae84e9439d4dfb5f6e2b08600fcf48a04710cc34"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"8484e65efeb2c9a35215af78d85384dea72c0a764a56f52bf811c979591f3ea0","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"dacc3052e422ef7fff1c6d6809977fef393ed7d0d9cd71ce9260a0ed87cd0c30","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"k83_KBd8VTJy2t-yKz2TPdTzLmEIlQ86BL0Kk9EGltO2aMJeGBgzdqga4PCj-MNzQaBYjHVnjYiwfyvyzJuTCQ"},"schema":"pubphys.envelope/1"},"record_hash":"8484e65efeb2c9a35215af78d85384dea72c0a764a56f52bf811c979591f3ea0","leaf_index":1016}