{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"398923e916bc2f52b14c35578df1a0c95146b6b962c0044b65ecc913ab92b30b","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b","d2728294983978acc523d07354f121efdf14ff6d3af22175f72b62f2baf83f74"],"salt":"960bad0b95a82786529efe13b8345398611917804b869690c24b9324adb87da8","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"yes-no","assisted_by":[],"external_id":"cm.cuprates.twisted-trsb","kind":"well-posed","literature_status":"contested","n":"2","parents":[],"plain":"Stacking two thin flakes of the cuprate Bi2Sr2CaCu2O8+x rotated by 45 degrees is predicted to create a superconducting state whose pairs circulate in one sense, breaking time-reversal symmetry; Josephson experiments by different groups disagree.","posed_since":"2021","precise":"For c-axis Josephson junctions between Bi2Sr2CaCu2O8+x flakes twisted by $\\theta$ near 45 degrees, pure $d_{(x^2-y^2)}$ pairing makes the first-order Josephson coupling vanish, and second-order coupling is predicted to stabilize a $d + i d$ state with spontaneous time-reversal breaking (Can et al., Nature Physics 2021). Determine whether the critical current $I_c(\\theta)$ is suppressed at 45 degrees as pure d-wave requires, and whether half-integer Shapiro steps, a Josephson diode effect and spontaneous magnetization near 45 degrees arise from time-reversal breaking rather than from interface disorder or an s-wave admixture. An answer is a reproducible $I_c(\\theta)$ on junctions with characterized interfaces plus a direct probe of time-reversal breaking at 45 degrees.","problem_ref":"d2728294983978acc523d07354f121efdf14ff6d3af22175f72b62f2baf83f74","references":"","settled_by":"Independent groups measuring $I_c(\\theta)$ on atomically sharp junctions, with local magnetometry or polar Kerr detection (or exclusion) of spontaneous time-reversal breaking at $\\theta = 45\\,\\mathrm{degrees}$.","status_note":"Zhao et al. (Science 2023) reported a Josephson diode effect and half-integer Shapiro steps near 45 degrees, while Zhu et al. (PRX 2021, PRB 2023) found Josephson tunneling persisting at 45 degrees across the doping dome and attributed it to s-wave pairing.","title":"Does 45-degree twisted $\\mathrm{Bi2Sr2CaCu2O8}+x$ break time-reversal symmetry?","topic_ref":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"f57403bd9a7a18aa06827c735e7fa103f54834bb4700fc2943dae5a045c2112f","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"fa5d575a2300799d3d7c3637f7d4bb783be01666a14ecab193a17c14a098cf5d","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"JlagM5eM3HXpcED87ImGPk2MTsXA8Dam5_c73VFlLx5vWgdTWlFDiVyP-nZMWVSqxdQ2UfAlGfhvrKGD1L3DCg"},"schema":"pubphys.envelope/1"},"record_hash":"f57403bd9a7a18aa06827c735e7fa103f54834bb4700fc2943dae5a045c2112f","leaf_index":2738}