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首页> 外文期刊>Physical review >Finite-temperature phase transition to a quantum spin liquid in a three-dimensional Kitaev model on a hyperhoneycomb lattice
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Finite-temperature phase transition to a quantum spin liquid in a three-dimensional Kitaev model on a hyperhoneycomb lattice

机译：在超蜂窝晶格上的三维Kitaev模型中有限温度相转变为量子自旋液体

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摘要

The quantum spin liquid is an enigmatic entity that is often hard to characterize within the conventional framework of condensed matter physics. We here present theoretical and numerical evidence for the characterization of a quantum spin liquid phase extending from the exact ground state to a finite critical temperature. We investigate a three-dimensional variant of the Kitaev model on a hyperhoneycomb lattice in the limit of strong anisotropy; the model is mapped onto an effective Ising-type model, where elementary excitations consist of closed loops of flipped Ising-type variables on a diamond lattice. Analyzing this effective model by Monte Carlo simulation, we find a phase transition from the quantum spin liquid to a paramagnet at a finite critical temperature T_c, accompanied by a divergent singularity of the specific heat. We also compute the magnetic properties in terms of the original quantum spins. We find that the magnetic susceptibility exhibits a broad hump above T_c, while it obeys the Curie law at high temperature and approaches a nonzero Van Vleck-type constant at low temperature. Although the susceptibility changes continuously at T_c, its temperature derivative shows a critical divergence at T_c. We also clarify that the dynamical spin correlation function is momentum independent but shows quantized peaks corresponding to discretized excitations. Although the phase transition accompanies no apparent symmetry breaking in terms of the Ising-type variables or of the original quantum spins, we characterize it from a topological viewpoint. We find that, by defining the flux density for loops of the Ising-type variables, the transition can be interpreted as one occurring from the zero-flux quantum spin liquid to the nonzero-flux paramagnet; the latter has a Coulombic nature due to the local constraints. The role of global constraints on the Ising-type variables is examined in comparison with the results in the two-dimensional loop model. The correspondence of our model to the Ising model on a diamond lattice is also discussed. A possible relevance of our results to the recently discovered hyperhoneycomb compound β-Li_2IrO_3 is mentioned.
机译：量子自旋液体是一个神秘的实体，通常很难在传统的凝聚态物理框架内进行表征。在这里，我们为量子自旋液相从精确基态延伸到有限临界温度的表征提供了理论和数值证据。我们在强各向异性的极限下研究了超蜂窝晶格上Kitaev模型的三维变体；该模型被映射到有效的伊辛型模型，其中基本激励由菱形晶格上翻转的伊辛型变量的闭环组成。通过蒙特卡洛模拟分析此有效模型，我们发现在有限的临界温度T_c下，从量子自旋液体到顺磁体的相变，伴随着比热的发散奇异性。我们还根据原始量子自旋来计算磁性。我们发现，磁化率在T_c上方表现出一个宽泛的驼峰，而在高温下服从居里定律，而在低温下却接近非零的Van Vleck型常数。尽管磁化率在T_c处连续变化，但其温度导数在T_c处显示出临界差异。我们还阐明了动态自旋相关函数与动量无关，但显示了与离散激励相对应的量化峰值。尽管相变没有伴随伊辛型变量或原始量子自旋的明显对称性破坏，但我们从拓扑学角度对其进行了表征。我们发现，通过为Ising型变量的环路定义通量密度，可以将过渡解释为从零通量量子自旋液体到非零通量顺磁体的转变。由于局部限制，后者具有库仑性质。与二维循环模型中的结果相比，检查了全局约束对Ising类型变量的作用。还讨论了我们的模型与菱形晶格上的Ising模型的对应关系。提到了我们的结果与最近发现的超蜂窝化合物β-Li_2IrO_3的可能相关性。

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  • 来源
    《Physical review》 |2014年第11期|115125.1-115125.13|共13页
  • 作者

    J. Nasu; T. Kaji; K. Matsuura; M. Udagawa; Y. Motome;

  • 作者单位

    Department of Applied Physics, University of Tokyo, Hongo, 7-3-1, Bunkyo, Tokyo 113-8656, Japan;

    Department of Applied Physics, University of Tokyo, Hongo, 7-3-1, Bunkyo, Tokyo 113-8656, Japan;

    Department of Advanced Materials Science, University of Tokyo, Kashiwa 277-8561, Japan;

    Department of Applied Physics, University of Tokyo, Hongo, 7-3-1, Bunkyo, Tokyo 113-8656, Japan;

    Department of Applied Physics, University of Tokyo, Hongo, 7-3-1, Bunkyo, Tokyo 113-8656, Japan;

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  • 正文语种 eng
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  • 关键词

    spin-orbit coupling, zeeman and stark splitting, jahn-teller effect; quantized spin models;

    机译：自旋轨道耦合;塞曼和斯塔克分裂;詹恩-泰勒效应;量化自旋模型;

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