Long-Range Order versus Random-Singlet Phases in Quantum Antiferromagnetic Systems with Quenched Disorder

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Abstract
The stability of antiferromagnetic long-range order against quenched disorder at zero temperature is considered. A simple model of an antiferromagnet with a spatially varying Néel temperature is shown to possess a nontrivial fixed point corresponding to long-range order that is stable unless either the order parameter or the spatial dimensionality exceeds a critical value. The instability of this fixed point corresponds to the system entering a random-singlet phase. The stabilization of long-range order is due to quantum fluctuations, whose influence on the phase diagram is discussed.