Topological Entanglement Entropy in the J1-J2 Quantum Antiferromagnet on a Square Lattice*

We employ exact diagonalization to calculate the ground state wave function of the next-nearest neighbor J1-J2 quantum antiferromagnet on a square lattice with 16 sites. Previous reports drawing attention to the magnetically frustrated regime in parameter space, roughly between 0.4 < J2/J1 < 0.6, have reported the presence of a valence bond crystal or gapless spin liquid phase. Using the Kitaev-Preskill Construction, we calculate a finite topological entanglement entropy (TEE) within this frustrated intermediate regime, suggesting the presence of a topologically ordered spin liquid phase.