Parallel Simulations of Phase Transitions in Disordered Many-Particle Systems

Phase transitions in classical and quantum many-particle systems are one of the most fascinating topics in contemporary condensed matter physics. The strong fluctuations associated with a phase transition or critical point can lead to unusual behavior and to novel, exotic phases in its vicinity, with consequences for problems such as quantum magnetism, unconventional superconductivity, non-Fermi liquid physics, and glassy behavior in doped semiconductors. In many realistic systems, impurities, dislocations, and other forms of quenched disorder play an important role. They often modify or even enhance the effects of the critical fluctuations. An interesting, if intricate, aspect of phase transitions with quenched disorder are the rare regions. These are large spatial regions that, due to a strong disorder fluctuation, are either devoid of impurities or have stronger interactions than the bulk system. They can be locally in one of the phases even though the bulk system may be in another phase. The slow fluctuations of these rare regions can dominate the behavior of the entire system.