Spin-Orbital Quantum Liquid on the Honeycomb Lattice
Spin-Orbital Quantum Liquid on the Honeycomb Lattice
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DOI：
10.1103/physrevx.2.041013
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发表时间：
2012-11-27
影响因子：
12.5
通讯作者：
Mila, Frederic
中科院分区：
文献类型：
--
作者：
Corboz, Philippe;Lajko, Miklos;Mila, Frederic
与带绝缘体相比，莫特绝缘体的主要特征是具有低能自旋涨落。此外，当晶体场能级被部分填充时，莫特绝缘体通常具有轨道自由度。虽然在大多数莫特绝缘体中，自旋和轨道发展了长程有序，但基态成为量子液体的可能性开辟了新的前景。本文给出了蜂窝晶格上Mott绝缘体的自旋轨道SU（4）对称Kugel-Khomskii模型是量子自旋轨道液体的明确证据。不存在任何形式的对称性破缺--晶格或SU（N）--得到了半经典和数值方法的支持：味波理论、张量网络算法和精确对角化。此外，这些方法所揭示的所有属性是非常准确地占投影变分波函数的基础上的π通量状态的费米子蜂窝晶格在1/4填充。在这种状态下，由于费米能级上存在狄拉克点，相关性是代数的，这表明蜂窝晶格上的对称库格尔-霍姆斯基模型是代数量子自旋轨道液体。这个模型提供了一个有趣的起点，了解最近发现的自旋轨道液体行为的Ba 3CuSb 2 O 9。目前的研究结果也表明，在超冷四色费米子原子中寻找量子液体时，选择具有蜂窝几何形状的光学晶格。
The main characteristic of Mott insulators, as compared to band insulators, is to host low-energy spin fluctuations. In addition, Mott insulators often possess orbital degrees of freedom when crystal-field levels are partially filled. While in the majority of Mott insulators, spins and orbitals develop long-range order, the possibility for the ground state to be a quantum liquid opens new perspectives. In this paper, we provide clear evidence that the spin-orbital SU(4) symmetric Kugel-Khomskii model of Mott insulators on the honeycomb lattice is a quantum spin-orbital liquid. The absence of any form of symmetry breaking-lattice or SU(N)-is supported by a combination of semiclassical and numerical approaches: flavor-wave theory, tensor network algorithm, and exact diagonalizations. In addition, all properties revealed by these methods are very accurately accounted for by a projected variational wave function based on the pi-flux state of fermions on the honeycomb lattice at 1/4 filling. In that state, correlations are algebraic because of the presence of a Dirac point at the Fermi level, suggesting that the symmetric Kugel-Khomskii model on the honeycomb lattice is an algebraic quantum spin-orbital liquid. This model provides an interesting starting point to understanding the recently discovered spin-orbital-liquid behavior of Ba3CuSb2O9. The present results also suggest the choice of optical lattices with honeycomb geometry in the search for quantum liquids in ultracold four-color fermionic atoms.