Deconfined criticality in the Shastry-Sutherland model

The Shastry-Sutherland model has recently attracted significant theoretical and experimental interest, particularly in materials like SrCu₂(BO₃)₂ due to its geometric frustration. A recent projective symmetry group classification revealed a gapless Z₂ spin liquid phase between the Néel and valence bond solid (VBS) phases, which is the equivalent of the square lattice Z2Azz13 spin liquid. We propose a deconfined SU(2) gauge theory to describe the transitions between Néel, VBS, and the tentative Z₂ spin liquid. By analyzing symmetry-allowed fermion bilinears we establish a connection between the square and Shastry-Sutherland lattices at the level of the critical theory. At the emergent SO(5) critical point, we compute critical exponents and assess stability via a large-flavor expansion. Our framework unifies the numerically observed Néel, Z₂ spin liquid, and VBS phases as a function of increasing J₂/J_1​, within a SU(2) gauge theory featuring Higgs fields and fermionic spinons.