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arXiv 2210.03752cond-mat.mes-hallcond-mat.str-el
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石墨烯$N=1$朗道能级对称性破缺量子霍尔态理论

Theory of broken symmetry quantum Hall states in the $N=1$ Landau level of Graphene

Nikolaos Stefanidis, Inti Sodemann Villadiego

摘要:

我们研究了石墨烯中$N=1$朗道能级的部分整数填充的多体基态,通过构建一个模型,该模型考虑了库仑相互作用的晶格尺度修正。有趣的是,与$N=0$ Landau水平相反,该模型不仅包含纯δ函数相互作用,而且包含其一些衍生物。由于这一点,我们发现几个重要的差异方面的$N=0$朗道水平。例如,在四分之一填充时,当仅填充单个组分时,存在量子霍尔铁磁体的简并提升,并且具有纠缠自旋和谷自由度的基态可以变得有利。此外,在$N=1$朗道能级的半填充处,我们发现了一个新的相位,该相位是在$N=0$朗道能级中不存在的,它结合了Kekulé态和反铁磁体的特征。我们还发现,根据在最近的实验中提取的参数,在半填充的$N=1$朗道能级石墨烯预计将在AF和CDW状态之间的微妙的竞争,但我们也讨论了为什么这些最近的实验模型可能会丢失一些重要的条款。

英文摘要:

We study many-body ground states for the partial integer fillings of the $N=1$ Landau level in graphene, by constructing a model that accounts for the lattice scale corrections to the Coulomb interactions. Interestingly, in contrast to the $N=0$ Landau level, this model contains not only pure delta function interactions but also some of its derivatives. Due to this we find several important differences with respect to the $N=0$ Landau level. For example at quarter filling when only a single component is filled, there is a degeneracy lifting of the quantum hall ferromagnets and ground states with entangled spin and valley degrees of freedom can become favourable. Moreover at half-filling of the $N=1$ Landau level, we have found a new phase that is absent in the $N=0$ Landau level, that combines characteristics of the Kekulé state and an antiferromagnet. We also find that according to the parameters extracted in a recent experiment, at half-filling of the $N=1$ Landau level graphene is expected to be in a delicate competition between an AF and a CDW state, but we also discuss why the models for these recent experiments might be missing some important terms.

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