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arXiv 1003.5679cond-mat.mes-hall
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填充因子为$ν=-1 $的双层石墨烯中的轨道有序

Orbital order in bilayer graphene at filling factor $ν=-1 $

R. Côté, Jules Lambert, Yafis Barlas, A. H. MacDonald

摘要:

在具有Bernal堆叠的石墨烯双层中,$n=0$和$n=1$轨道朗道能级都具有零动能。因此,N=0朗道能级中的电子态除了其引导中心标记之外还具有三个量子数:其自旋,其谷指数$K$或$K^{\prime}$,和轨道量子数$n=0,1.$。双层中的二维电子气(2DEG)支持各种各样的断裂-其中赝自旋以依赖于填充因子$ν$和电势差两者的方式使这三个量子数有序化的对称状态在层之间。在本文中,我们研究了$ν=-1$在强到足以冻结电子自旋的外场中的情况。我们发现,层之间的电势差驱动一系列的过渡,从层间相干态(ICS)在小的电位,并导致轨道相干态(OCS),在一个单一的层极化。轨道赝自旋携带电偶极子,其方向在OCS中是有序的,并且具有Dzyaloshinskiii-Moriya相互作用,可以导致螺旋不稳定性。我们发现,ICSs,OCSs,以及在中间电位发生的混合态的微波吸收光谱是截然不同的。

英文摘要:

In a graphene bilayer with Bernal stacking both $n=0$ and $n=1$ orbital Landau levels have zero kinetic energy. An electronic state in the N=0 Landau level consequently has three quantum numbers in addition to its guiding center label: its spin, its valley index $K$ or $K^{\prime}$, and an orbital quantum number $n=0,1.$ The two-dimensional electron gas (2DEG) in the bilayer supports a wide variety of broken-symmetry states in which the pseudospins associated these three quantum numbers order in a manner that is dependent on both filling factor $ν$ and the electric potential difference between the layers. In this paper, we study the case of $ν=-1$ in an external field strong enough to freeze electronic spins. We show that an electric potential difference between layers drives a series of transitions, starting from interlayer-coherent states (ICS) at small potentials and leading to orbitally coherent states (OCS) that are polarized in a single layer. Orbital pseudospins carry electric dipoles with orientations that are ordered in the OCS and have Dzyaloshinskii-Moriya interactions that can lead to spiral instabilities. We show that the microwave absorption spectra of ICSs, OCSs, and the mixed states that occur at intermediate potentials are sharply distinct.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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