Vacancy-Induced Low-Energy Density of States in the Kitaev Spin Liquid
Vacancy-Induced Low-Energy Density of States in the Kitaev Spin Liquid
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DOI：
10.1103/physrevx.11.011034
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发表时间：
2021-02-18
影响因子：
12.5
通讯作者：
Perkins, Natalia B.
中科院分区：
文献类型：
--
作者：
Kao, Wen-Han;Knolle, Johannes;Perkins, Natalia B.
Kitaev蜂窝模型由于其具有分数化Majorana激发的自旋液体基态的精确可解性及其在具有强自旋轨道耦合的磁性Mott绝缘体中的可能实现而引起了人们的极大关注。最近，5d电子化合物H3LiIr2O6被证明是Kitaev物理的强有力候选者，考虑到没有任何长程有序磁态的迹象。在这项工作中，我们证明了Kitaev模型中的随机空位的有限密度引起了低能量Majorana本征模的惊人堆积，并再现了H3LiIr2O6的比热测量中的明显幂律上升。在物理上，空位可以来自各种来源，例如缺失的磁矩或杂质的存在（真空位），或者由于强但罕见的键随机性（准空位）而导致的磁矩的局部弱耦合。我们数值计算表明，空位效应是很容易检测到的，即使在低空位浓度，它不是很敏感的性质的空位或不同的磁通背景。我们还研究了现场稀释Kitaev自旋液体的三自旋相互作用项，打破时间反演对称性和模仿外部磁场的响应。我们提出了一个领域引起的磁通扇区转变的基态成为磁通自由较大的领域，导致在一个明确的抑制低温比热。最后，我们讨论了悬挂的马约拉纳费米子在真正的空缺的情况下的效果，并表明，他们的耦合到一个外加磁场通过塞曼相互作用也可以占在H3LiIr2O6中观察到的高场极限的标度行为。
The Kitaev honeycomb model has attracted significant attention due to its exactly solvable spin-liquid ground state with fractionalized Majorana excitations and its possible materialization in magnetic Mott insulators with strong spin-orbit couplings. Recently, the 5d-electron compound H3LiIr2O6 has shown to be a strong candidate for Kitaev physics considering the absence of any signs of a long-range ordered magnetic state. In this work, we demonstrate that a finite density of random vacancies in the Kitaev model gives rise to a striking pileup of low-energy Majorana eigenmodes and reproduces the apparent power-law upturn in the specific heat measurements of H3LiIr2O6. Physically, the vacancies can originate from various sources such as missing magnetic moments or the presence of nonmagnetic impurities (true vacancies), or from local weak couplings of magnetic moments due to strong but rare bond randomness (quasivacancies). We show numerically that the vacancy effect is readily detectable even at low vacancy concentrations and that it is not very sensitive either to the nature of vacancies or to different flux backgrounds. We also study the response of the site-diluted Kitaev spin liquid to the three-spin interaction term, which breaks time-reversal symmetry and imitates an external magnetic field. We propose a field-induced flux-sector transition where the ground state becomes flux-free for larger fields, resulting in a clear suppression of the low-temperature specific heat. Finally, we discuss the effect of dangling Majorana fermions in the case of true vacancies and show that their coupling to an applied magnetic field via the Zeeman interaction can also account for the scaling behavior in the high-field limit observed in H3LiIr2O6.