Has a Dirac spin liquid been realized in a material?
In plain words
In a Dirac spin liquid the spinons have energies growing linearly with momentum near a few points, so the neutron signal rises linearly with energy and forms cones. Candidates have been reported in kagome and triangular compounds, but confirmation in independent materials is lacking.
Precise statement
In candidate materials (kagome YCu3(OH)6Br2[Br_x(OH)_1-x], triangular Yb-based compounds), establish the $U(1)$ Dirac spin liquid by its signatures: a dynamic structure factor $S(q,\omega)$ with conical continua at the predicted momenta and low-energy intensity $\sim \omega$, a magnetic heat capacity $C\sim T^2$, and monopole excitations at the predicted momenta. An answer is a material in which at least two such signatures are reproduced across samples and match a parton or numerical calculation of the Dirac spin liquid on that lattice.
What would settle it
Inelastic neutron scattering with resolution below 0.1 J resolving conical continua, plus heat capacity and thermal conductivity down to about 0.05 K, on crystals with characterized site disorder.
Status in the literature
Unverified note
Zeng et al. (Nature Physics 2024, arXiv:2310.11646) reported conical spinon continua in YCu3(OD)6Br2[Br_0.33(OD)_0.67]; confirmation in independent compounds is lacking.