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arXiv 2104.02182cond-mat.str-el
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Kitaev模型中的Majorana关联

Majorana correlations in the Kitaev model with ordered-flux structures

Akihisa Koga, Yuta Murakami, Joji Nasu

摘要:

研究了蜂窝格子上$S=1/2$ Kitaev模型中磁通组态对出射Majorana费米子的影响,其中量子自旋被分解为巡游的Majorana费米子和局域磁通.在Kitaev模型的无通量区出现了量子自旋液体作为其基态,这一现象一直是人们研究的热点。在这个通量扇区中,马约拉纳费米子系统具有线性色散,并在马约拉纳关联中表现出幂律行为。另一方面,在Majorana费米子系统中,纵向排列的磁通组态产生低能激发,这与无磁通状态下的激发明显不同。我们发现,周期性排列的通量状态之一的结果在缺口马约拉纳色散和指数衰减的马约拉纳相关。具有另一种磁通组态的Kitaev系统表现出半Dirac色散,导致沿对称轴的幂律衰减,其幂次比无磁通扇区中的幂次小。我们还研究了通量配置的随机性的影响,并澄清,马约拉纳密度的状态填充通过增加通量密度,幂律衰减的马约拉纳相关性仍然存在。目前的结果可能是重要的,以控制运动的马约拉纳费米子,携带自旋激发,在Kitaev候选材料。

英文摘要:

We study the effects of the flux configurations on the emergent Majorana fermions in the $S=1/2$ Kitaev model on a honeycomb lattice, where quantum spins are fractionalized into itinerant Majorana fermions and localized fluxes. A quantum spin liquid appears as the ground state of the Kitaev model in the flux-free sector, which has intensively been investigated so far. In this flux sector, the Majorana fermion system has linear dispersions and shows power law behavior in the Majorana correlations. On the other hand, periodically-arranged flux configurations yield low-energy excitations in the Majorana fermion system, which are distinctly different from those in the flux-free state. We find that one of the periodically arranged flux states results in the gapped Majorana dispersion and the exponential decay in the Majorana correlations. The Kitaev system with another flux configuration exhibits a semi-Dirac like dispersion, leading to the power law decay with a smaller power than that in the flux-free sector along symmetry axes. We also examine the effect of the randomness in the flux configurations and clarify that the Majorana density of states is filled by increasing the flux density, and power-law decay in the Majorana correlations remains. The present results could be important to control the motion of Majorana fermions, which carries the spin excitations, in the Kitaev candidate materials.

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