{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"1c997727e86347c0327036b7479647c689e1f5e6e72fe6c02ed682ea56f99caa","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":["ai:gpt-5.5"],"kind":"seed"},"parents":["8484e65efeb2c9a35215af78d85384dea72c0a764a56f52bf811c979591f3ea0","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"9739a2673bc87f6d8284d8cc71bb4bf6fb9fb1b8b140757112de512ad0455901","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"identification","assisted_by":["ai:gpt-5.5"],"external_id":"cm.heavy-fermions.uru2si2-hidden-order","kind":"well-posed","literature_status":"contested","n":"2","parents":[],"plain":"Below 17.5 K, $\\mathrm{URu_2Si_2}$ 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 $\\mathrm{URu_2Si_2}$, 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":"8484e65efeb2c9a35215af78d85384dea72c0a764a56f52bf811c979591f3ea0","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 $\\mathrm{URu_2Si_2}$?","topic_ref":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"ddf0bbf01604d40d03be88b6b0c629c7793296d8dd5de7497a1dce0796e560a8","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"c6ea849ddd657355404bba623ace919ca793800d986533bd495a4c0389431a1b","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"OwyxbW5XZc1tBjEgqFZPyXVqWUXGQxPsCh8fo4t_l1EUt88or4NkF0EXgxsA3BJ7ntraZKbAXIlj-PTzIqPnBQ"},"schema":"pubphys.envelope/1"},"record_hash":"ddf0bbf01604d40d03be88b6b0c629c7793296d8dd5de7497a1dce0796e560a8","leaf_index":2844}