Z₂ Dirac Spin Liquid in the Shastry-Sutherland model

We investigate the nature of the quantum spin liquid (QSL) phase in the spin S=1/2 Heisenberg antiferromagnet on the Shastry-Sutherland lattice. Our DMRG analysis indicates that this QSL is adiabatically connected to the square lattice J₁-J₂ QSL. We thus perform a projective symmetry group (PSG) classification of fermionic mean-field Ansätze and establish their connection to the square lattice PSGs, to identify a gapless Z₂ Dirac QSL as a promising candidate for ground state. Performing a state-of-the-art variational Monte Carlo analysis supplemented with Lanczos steps, we demonstrate its energetic competitiveness and agreement of correlation functions with previous DMRG and neural network based studies. We also present the dynamical spin structure factors obtained from a Keldysh pseudo-fermion functional renormalization group analysis which supports the scenario of a Z₂ Dirac QSL.