Quantum Criticality and Deconfinement in Phase Transitions Between Valence Bond Solids
Quantum Criticality and Deconfinement in Phase Transitions Between Valence Bond Solids
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DOI：
10.1103/physrevb.69.224416
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发表时间：
2003-11
影响因子：
3.7
通讯作者：
A. Vishwanath;L. Balents;T. Senthil
中科院分区：
文献类型：
--
作者：
A. Vishwanath;L. Balents;T. Senthil
我们考虑自旋半量子反铁磁体在两个空间维度的量子极限，其中的自旋是在一个价键固体（VBS）相。两个这样的VBS阶段之间的过渡进行了研究。在某些情况下，一个有趣的二阶跃迁被发现由一个固定的线与不同的临界指数控制。一个具体的例子是提供了一个反铁磁耦合双层系统的蜂窝晶格，其中连续的量子相变可以普遍存在于两个VBS相之间。此外，这些临界点是取消限制的，在这个意义上说，有间隙的自旋1自旋2自旋子激发出现在过渡的权利。这个临界点的低能物理学（直到边缘不相关的相互作用）只包含一个自由的二次色散光子。在这个连续过渡的一侧的相位结构是非常复杂的，由一系列以“魔鬼楼梯”形式无限紧密间隔的进一步过渡组成。类比与以前的例子去限制量子临界性的强调。单层系统中密切相关的过渡进行了探讨。这些只是在某些多临界点上的二阶。单层系统量子二聚体模型的可解Rokshar-Kivelson点对应于一个非一般的多临界点。
We consider spin-half quantum antiferromagnets in two spatial dimensions in the quantum limit, where the spins are in a valence bond solid (VBS) phase. The transition between two such VBS phases is studied. In some cases, an interesting second-order transition controlled by a fixed line with varying critical exponents is found. A specific example is provided by an antiferromagnetically coupled bilayer system on the honeycomb lattice where a continuous quantum phase transition can generically exist between two VBS phases. Furthermore, these critical points are deconfined, in the sense that gapped spin-$1∕2$ spinon excitations emerge right at the transition. The low-energy physics of this critical point (up to marginally irrelevant interactions) contains just a free quadratically dispersing ``photon.'' The phase structure on one side of this continuous transition is very intricate, consisting of a series of infinitely closely spaced further transitions in a ``devil's staircase'' form. Analogies with previous examples of deconfined quantum criticality are emphasized. Closely related transitions in single layer systems are explored. These are second order only at some multicritical points. The solvable Rokshar-Kivelson point of quantum dimer models of single layer systems is found to correspond to a nongeneric multicritical point.