{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"3027628e0db6732970e5765b179f5a481a19b3bff3807134d79cb25b182d2989","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["7bfab33914c189112dcaa847b4aca6e64c0537f0e0833294939c4e9a412b517b","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"efe4546d26c45320b4ba9cff210cdb88cc56df9cf2b107dd011355bdf08d555b","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"yes-no","assisted_by":[],"external_id":"cm.weyl-semimetals.axion-cdw","kind":"well-posed","literature_status":"contested","n":"2","parents":[],"plain":"When a charge-density wave (a periodic ripple in electron density) gaps out the Weyl points of (TaSe4)2I, its sliding motion should act like the hypothetical axion particle; one experiment reported this and later work questioned it.","posed_since":"2019","precise":"Gooth et al. (Nature 575, 315, 2019, doi:10.1038/s41586-019-1630-4) reported a positive magnetoconductance of the sliding charge-density wave in (TaSe4)2I for E parallel to B, attributed to the phason (sliding mode) acting as a dynamical axion field $\\theta(r,t)$ coupled to E.B; Sinchenko et al. (Applied Physics Letters, 2022, doi:10.1063/5.0080380) questioned this interpretation. Determine whether the charge-density-wave phase is an axion insulator with dynamical $\\theta$: the test is a phason-carried response proportional to E.B, absent for E perpendicular to B, with magnitude set by the number of Weyl-node pairs. An answer is yes or no with that quantitative comparison.","problem_ref":"7bfab33914c189112dcaa847b4aca6e64c0537f0e0833294939c4e9a412b517b","references":"","settled_by":"Angle-resolved nonlinear transport of the sliding mode with independent control of E and B on several samples, plus spectroscopic measurement of the phason mass and its coupling to light.","status_note":"Questioned in 2022; a 2023 Nature Materials study (Kim et al., doi:10.1038/s41563-023-01504-5) observed a massive phason in (TaSe4)2I, consistent with but not proof of axion dynamics.","title":"Is the charge-density wave in (TaSe4)2I an axion insulator?","topic_ref":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"1e73c73e84e9bd223320a36c3de79f70e11f7c56e49a8b5d68caf1fb00b3cdbf","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"954a447330a029411268287ee84bf82be1eaaf6c22ea5f5564df310058c9678f","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"xXjEfLhcapqQsLq4bfNKD9K3dwKcEOP1sa0jU24HmZljRwkxWJi5xVC82vvZid15ReEaPfpJcztPQsuXS2W9Bw"},"schema":"pubphys.envelope/1"},"record_hash":"1e73c73e84e9bd223320a36c3de79f70e11f7c56e49a8b5d68caf1fb00b3cdbf","leaf_index":3100}