{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"08a6156fd27d0b739c9855a1573f993a7c680815c28598b4fd66d27a5fa2e8f5","created":"2026-10-03T07:18:00Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"9487ba2688c62e98756b9d8d9f87e4ae02fa646556919080dcc648f8548eef7e","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"identification","assisted_by":[],"external_id":"cm.magnetic-topological-insulators.axion-state-mnbi2te4","kind":"well-posed","literature_status":"contested","n":"1","parents":[],"plain":"Thin MnBi2Te4 with an even number of layers shows zero Hall resistance and high longitudinal resistance at zero field, which fits an axion insulator but also an ordinary insulator.","posed_since":"2019","precise":"For even-layer MnBi2Te4 in its antiferromagnetic ground state, determine whether $\\theta = \\pi$, with half-quantized surface Hall conductance $\\pm e^{2}/(2h)$ on the top and bottom surfaces, or whether the state is trivial ($\\theta = 0$). The zero Hall plateau alone does not discriminate. An answer is an identification from a surface-resolved or theta-sensitive measurement.","problem_ref":null,"references":"","settled_by":"Layer-resolved Kerr or Faraday rotation, nonlocal transport, or a magnetoelectric measurement isolating the $\\theta = \\pi$ response.","status_note":"","title":"Is even-layer MnBi2Te4 an axion insulator","topic_ref":"eef15c72032faa1168fa9014695d510856a871a88df07cd67b817c3027aab793"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"c937df08022b433413d0538c4b3e4094b5e3e9cb171a8a5f61f508de476e6213","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"9a70f4c0b27f48e2fadb6cc5cc281ba6d45fa1786063287f466c61a71f2ad9f2","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"piXWRXmFJf4yUa0kLPGg2nBnqvDJYgbIb76t_m_RvEVOtEpE_WMawN7df7qWma0nBSl0Rc2X-c1ZxRPbQw8CAQ"},"schema":"pubphys.envelope/1"},"record_hash":"c937df08022b433413d0538c4b3e4094b5e3e9cb171a8a5f61f508de476e6213","leaf_index":1074}