Chiral Spin Liquid on a Shastry-Sutherland Heisenberg Antiferromagnet

We demonstrate the existence of a topological chiral spin liquid in the frustrated Shastry-Sutherland Heisenberg model with an additional spin chirality interaction, using numerically unbiased exact diagonalization and density matrix renormalization group methods. We establish a quantum phase diagram where conventional phases, including dimer singlet, plaquette singlet, Néel and collinear phase, can be clearly identified by suitable local order parameters. Among them a SU(2)_1 chiral spin liquid emerges in the highly frustrated region, which is unambiguously identified by two topologically degenerate ground states, modular matrix, and characteristic level counting in entanglement spectrum, featuring the same topological order of ν=1/2 bosonic Laughlin state. The phase boundaries among the different orders are determined by the energy level crossing analysis and wave function fidelity susceptibility.