Spin liquid between plaquette and Neel phases of Shastry-Sutherland model
In plain words
The Shastry-Sutherland model, which describes the layered magnet SrCu2(BO3)2, changes from a state of spin singlets on squares (plaquettes) to Neel magnetic order as a coupling ratio grows. Calculations disagree on whether a narrow spin-liquid phase lies between the two or they meet directly.
Precise statement
H = J sum_dimers S_i . S_j + J' sum_<ij> S_i . S_j, $S = 1/2$, Shastry-Sutherland lattice, J the intradimer and J' the interdimer coupling. For $J'/J$ of about 0.76 to 0.83, determine whether a gapless spin-liquid phase separates the plaquette valence-bond solid from the Neel phase or the transition is direct (weakly first order or deconfined critical), and give the phase boundaries. An answer gives the extrapolated Neel moment and plaquette order parameter across the window with error bars.
What would settle it
Agreement between iPEPS, DMRG with pinning-field finite-size scaling and neural-network variational states on the extrapolated Neel moment and plaquette order across the window.
Status in the literature
Unverified note
Corboz, Zhang, Ponsioen and Mila (PRL 2026, arXiv:2502.14091) found a spin liquid for $0.785 \le J'/J \le 0.82$, while DMRG with pinning fields (Lv, Qian, Qin, arXiv:2609.22907, 2026) found finite Neel order across that region and a direct transition.