Department of Physics, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, USA.
Phys Rev Lett. 2010 Apr 30;104(17):177201. doi: 10.1103/PhysRevLett.104.177201. Epub 2010 Apr 26.
The antiferromagnetic to valence-bond-solid phase transition in the two-dimensional J-Q model (an S=1/2 Heisenberg model with four-spin interactions) is studied using large-scale quantum Monte Carlo simulations. The results support a continuous transition of the ground state, in agreement with the theory of "deconfined" quantum criticality. There are, however, large corrections to scaling, of logarithmic or very slowly decaying power-law form, which had not been anticipated. This suggests that either the SU(N) symmetric noncompact CP;{N-1} field theory for deconfined quantum criticality has to be revised or that the theory for N=2 (as in the system studied here) differs significantly from N-->infinity (where the field theory is analytically tractable).
利用大规模量子蒙特卡罗模拟研究了二维 J-Q 模型（具有四自旋相互作用的 S=1/2 海森堡模型）中的反铁磁到价带固体相变。结果支持基态的连续相变，与“去禁闭”量子临界点理论一致。然而，存在很大的标度修正，呈对数或非常缓慢衰减的幂律形式，这是之前没有预料到的。这表明，去禁闭量子临界点的 SU(N)对称非紧致 CP{N-1}场论必须进行修正，或者 N=2 的理论（如本文研究的系统）与 N→∞（此时场论可解析处理）有显著差异。
