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Mott glass in site-diluted S=1 antiferromagnets with single-ion anisotropy

The interplay between site dilution and quantum fluctuations in S=1 Heisenberg antiferromagnets on the square lattice is investigated using quantum Monte Carlo simulations. Quantum fluctuations are tuned by a single-ion anisotropy D. In the clean limit, a sufficiently large D>D_c = 5.65(2) J forces each spin into its m_S=0 state, and thus destabilizes antiferromagnetic order. In the presence of site dilution, quantum fluctuations are found to destroy Néel order before the percolation threshold of the lattice is reached, if D exceeds a critical value D^* = 2.3(2) J. This mechanism opens up an extended quantum-disordered Mott glass phase on the percolated lattice, characterized by a gapless spectrum and vanishing uniform susceptibility.