Quantum phase transitions in coupled dimer compounds

We study the critical properties in cubic systems of antiferromagnetically coupled spin dimers near magnetic-field-induced quantum phase transitions. The quantum critical points in the zero-temperature phase diagram are determined from quantum Monte Carlo simulations. Furthermore, scaling properties of the uniform magnetization and the staggered transverse magnetization across the quantum phase transition in magnetic fields are calculated. Excellent agreement is observed between the quantum Monte Carlo simulations and previous analytical and experimental results near the magnetic field-induced transition. At the zero-field quantum critical point, logarithmic corrections to mean-field behavior are observed, which match well recent experiments for the pressure-induced quantum phase transition.