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arXiv 1708.03050cond-mat.str-el
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非限定量子临界点附近的涌现对称性和三临界点

Emergent Symmetry and Tricritical Points near the deconfined Quantum Critical Point

Chao-Ming Jian, Alex Rasmussen, Yi-Zhuang You, Cenke Xu

摘要:

最近提出的$N=2$非紧QED $_3$和易平面非紧CP $^1$(NCCP $^1$)模型之间的对偶性表明,由于$N=2$非紧QED $_3$的自对偶性,易平面反铁磁体和正方形晶格上VBS阶之间的解限定量子临界点(dQCP)可能具有涌现的O(4)对称性。最近的数值研究表明,这种易平面dQCP确实存在,并且具有O(4)对称性。但是为了使O(4)对称性真正出现在dQCP上,某些O(4)对称性破缺扰动需要在假定的O(4)不动点上是无关的。在$N=2$非紧QED $_3$中研究这些对称破缺微扰更为方便。我们证明了自然的大$N$推广和受控的$1/N$展开支持O(4)不动点对对称破缺扰动的稳定性。我们还发展了两个三临界点接近易平面dQCP的理论。一个三临界点在dQCP和{ \it自对偶} $Z_2$拓扑序之间;另一个是连接连续dQCP和一阶Néel-VBS跃迁的三临界点,这是由最近的数值结果激发的。

英文摘要:

Recent proposal of the duality between the $N=2$ noncompact QED$_3$ and the easy-plane noncompact CP$^1$ (NCCP$^1$) model suggests that the deconfined quantum critical point (dQCP) between the easy-plane antiferromagnet and the VBS order on the square lattice may have an emergent O(4) symmetry, due to the self-duality of the $N=2$ noncompact QED$_3$. Recent numerical progresses suggest that this easy-plane dQCP does exist and it has an emergent O(4) symmetry. But for the O(4) symmetry to really emerge at the dQCP, certain O(4) symmetry breaking perturbations need to be irrelevant at the putative O(4) fixed point. It is more convenient to study these symmetry breaking perturbations in the $N=2$ noncompact QED$_3$. We demonstrate that a natural large-$N$ generalization and a controlled $1/N$ expansion supports the stability of the O(4) fixed point against the symmetry breaking perturbations. We also develop the theory for two tricritical points close to the easy-plane dQCP. One tricritical point is between the dQCP and a {\it self-dual} $Z_2$ topological order; the other is the tricritical point that connects the continuous dQCP and a first order Néel-VBS transition, motivated by recent numerical results.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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