Prokof'ev Nikolay, Svistunov Boris
Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003, USA.
Phys Rev Lett. 2004 Jan 9;92(1):015703. doi: 10.1103/PhysRevLett.92.015703. Epub 2004 Jan 8.
We report results of large-scale Monte Carlo simulations of superfluid-insulator transitions in disordered commensurate 2D bosonic systems. In the off-diagonal disorder case, we find that the transition is to a gapless incompressible insulator, and its dynamical critical exponent is z=1.5(2). In the diagonal-disorder case, we prove the conjecture that rare statistical fluctuations are inseparable from critical fluctuations on the largest scales and ultimately result in crossover to the generic universality class (apparently with z=2). However, even at strong disorder, the universal behavior sets in only at very large space-time distances. This explains why previous studies of smaller clusters mimicked a direct superfluid-Mott-insulator transition.
我们报告了无序相称二维玻色子系统中超流-绝缘体转变的大规模蒙特卡罗模拟结果。在非对角无序情况下，我们发现转变为无隙不可压缩绝缘体，其动力学临界指数为z = 1.5(2)。在对角无序情况下，我们证明了这样一个猜想：罕见的统计涨落与最大尺度上的临界涨落不可分割，最终导致向一般普适类的交叉（显然z = 2）。然而，即使在强无序情况下，普适行为也仅在非常大的时空距离处才出现。这解释了为什么之前对较小团簇的研究模拟了直接的超流-莫特绝缘体转变。
