Yasir Iqbal
(Indian Institute of Technology Madras)

We present a multimethod investigation into the nature of the recently reported quantum spin liquid (QSL) phase in the spin-1/2 Heisenberg antiferromagnet on the Shastry-Sutherland lattice. A comprehensive projective symmetry group classification of fermionic mean-field Ansätze on this lattice yields 46 U(1) and 80 ℤ2 states. Motivated by density-matrix renormalization group (DMRG) calculations suggesting that the Shastry-Sutherland model and the square-lattice J1-J2 Heisenberg antiferromagnet putatively share the same QSL phase, we establish a mapping of our Ansätze to those of the square lattice. This enables us to identify the equivalent of the square-lattice QSL (Z2Azz13) in the Shastry-Sutherland system. Employing state-of-the-art variational Monte Carlo calculations with Gutzwiller-projected wavefunctions improved upon by Lanczos steps, we demonstrate the excellent agreement of energies and correlators between a gapless (Dirac) ℤ2 spin liquid -- characterized by only few parameters -- and approaches based on neural quantum states and DMRG. Furthermore, the real-space spin-spin correlations are shown to decay with the same power law as in the J1-J2 square lattice model, which also hosts a ℤ2 Dirac spin liquid. Finally, we apply the recently developed Keldysh formulation of the pseudo-fermion functional renormalization group to compute the dynamical spin structure factor; these correlations exhibit the features expected due to Dirac cones in the excitation spectrum, thus providing strong independent evidence for a Dirac QSL ground state. Our finding of a d-wave pairing ℤ2 Dirac QSL is consistent with the recently observed signatures of QSL behavior in Pr2Ga2BeO7 and outlines predictions for future experiments.

Zoom registration link:
https://zoom.us/meeting/register/rwIL4MlHSpmze4NHETHAIw