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Title: Superfluid fraction tensor of a two-dimensional dipolar supersolid
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.
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.
Settled by: A 2D measurement of $f_s$ along two lattice directions compared with Leggett bounds from in-situ imaging.
Kind: well-posed
Answer type: value
References: (empty)
Literature status: partially-resolved
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).
Posed since: (empty)