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arXiv 0812.3657cond-mat.str-elcond-mat.stat-mech
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正方格点上SU(N)Heisenberg模型的连续N量子Monte Carlo研究

The SU(N) Heisenberg model on the square lattice: a continuous-N quantum Monte Carlo study

K. S. D. Beach, Fabien Alet, Matthieu Mambrini, Sylvain Capponi

摘要:

一个量子相变通常是通过调整一个外部参数,出现在一个耦合常数的哈密顿诱导。另一种途径是改变系统的全局对称性,例如,SU(2)到SU(N)。然而,在这种情况下,控制参数的离散性质阻止人们识别和表征过渡。我们展示了如何克服这一限制的SU(N)海森堡模型的帮助下,单重投影算法,可以连续处理N。在正方形晶格上,我们发现在Nc=4.57(5)处Neel有序相和晶体键序相之间存在直接的、连续的相变,临界指数z=1,β/nu=0.81(3)。

英文摘要:

A quantum phase transition is typically induced by tuning an external parameter that appears as a coupling constant in the Hamiltonian. Another route is to vary the global symmetry of the system, generalizing, e.g., SU(2) to SU(N). In that case, however, the discrete nature of the control parameter prevents one from identifying and characterizing the transition. We show how this limitation can be overcome for the SU(N) Heisenberg model with the help of a singlet projector algorithm that can treat N continuously. On the square lattice, we find a direct, continuous phase transition between Neel-ordered and crystalline bond-ordered phases at Nc=4.57(5) with critical exponents z=1 and beta/nu=0.81(3).

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