{"schema":"pubphys.bundle/1","record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"d3fa65525952864834dff903116f9f2c61cd4d23ce8d8edb8eef4d39995b6064","created":"2026-10-03T07:17:59Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"a3227955371873b6e10b8cd041c7b8bdfd0f137ae95555e3ff9e2e21c7a4657e","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"yes-no","assisted_by":[],"external_id":"cm.excitonic-insulators.tmd-exciton-superfluid","kind":"well-posed","literature_status":"open","n":"1","parents":[],"plain":"In two semiconductor layers separated by a thin insulator, electrons in one layer and holes in the other bind into long-lived excitons and make the system insulating. Drag experiments show these excitons move as units, but frictionless superflow has not been shown.","posed_since":"","precise":"In MoSe2/hBN/WSe2 electron-hole double layers at equal densities $n_e = n_h$ of order $1e11 \\text{ to } 1e12\\,\\mathrm{cm}^{-2}$, 2025 Coulomb-drag experiments found a drag ratio near 1 (perfect drag), showing transport by bound excitons. Determine whether the exciton fluid has a finite superfluid stiffness below a Berezinskii-Kosterlitz-Thouless temperature $T_{\\mathrm{BKT}}$, i.e. vanishing counterflow resistance or a Josephson-like interlayer response, and give $T_{\\mathrm{BKT}}$ versus density. An answer is yes or no with measured $T_{\\mathrm{BKT}}(n)$.","problem_ref":null,"references":"","settled_by":"A counterflow transport measurement showing resistance vanishing below a density-dependent $T_{\\mathrm{BKT}}$, or a bound on stiffness excluding superfluidity down to the lowest accessible temperature.","status_note":"Two 2025 Science papers (Nguyen et al.; Qi et al.) reported perfect Coulomb drag, establishing exciton transport but not superfluidity.","title":"Is the MoSe2/WSe2 dipolar excitonic insulator an exciton 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