{"schema":"pubphys.bundle/1","record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"fa83c6cfa16eb3843d6f9f08cae2c0bf662bb11fb32005aa46f58c440ee6a231","created":"2026-10-03T07:17:53Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"cb879978f1795360621038740cfb4941876f0c477ef8947a2731a36c59d37f28","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":[],"external_id":"amo.dipolar-supersolids.superfluid-fraction-2d","kind":"well-posed","literature_status":"partially-resolved","n":"1","parents":[],"plain":"In a supersolid only part of the matter flows freely (the superfluid fraction). It has been measured in a chain of droplets, but not in a two-dimensional crystal where it can depend on direction.","posed_since":"","precise":"For a 2D triangular or honeycomb supersolid of Dy-164 or Er-166, measure the superfluid fraction tensor f_s,ij (via Josephson oscillations, moment of inertia or sound speeds) as a function of density contrast, and compare with Leggett's upper and lower bounds computed from the measured density profile. Answer: f_s,ij versus contrast with errors.","problem_ref":null,"references":"","settled_by":"A 2D measurement of $f_s$ along two lattice directions compared with Leggett bounds from in-situ imaging.","status_note":"A 2024 Josephson-effect measurement in a one-dimensional droplet array found a sub-unity fraction consistent with the Leggett bound (Biagioni et al., Nature 2024; arXiv:2311.04757).","title":"Superfluid fraction tensor of a two-dimensional dipolar 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