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arXiv 2105.02415cond-mat.str-elcond-mat.mes-hallcond-mat.supr-con
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具有常规和高阶Van Hove奇异性的Moire过渡金属二硫族化物的自旋谷锁定不稳定性

Spin-valley locked instabilities in moire transition metal dichalcogenides with conventional and higher-order Van Hove singularities

Yi-Ting Hsu, Fengcheng Wu, S. Das Sarma

摘要:

最近的实验已经观察到相关的绝缘和可能的超导相在扭曲的同质双层过渡金属二硫属化物(TMD)。除了由于固有的伊辛自旋轨道耦合的自旋谷锁定的莫尔带,同质双层莫尔TMD还具有对数或幂律发散的范霍夫奇点(VHS)附近的费米面,可控制的外部位移场。前者和后者分别被称为传统和高阶VHS。在这里,我们进行了微扰重整化群(RG)分析,无偏地研究占主导地位的不稳定性,在同双层TMD的常规和高阶VHS的情况下。我们发现,自旋谷锁定在很大程度上改变了RG流,并导致意外的不稳定性,在相应的广泛研究的石墨烯为基础的莫尔系统,如自旋和谷极化铁磁性和拓扑超导混合宇称。特别是,对于两个高阶VHS的情况下,我们发现一个自旋谷锁定驱动的金属态没有对称性破缺的TMD,尽管发散裸磁化率。我们的研究结果显示了自旋谷锁定如何显着影响RG分析,并表明莫尔TMD是实现各种相互作用引起的自旋谷锁定相的合适平台,突出了与研究充分的石墨烯基莫尔系统根本不同的物理学。

英文摘要:

Recent experiments have observed correlated insulating and possible superconducting phases in twisted homobilayer transition metal dichalcogenides (TMDs). Besides the spin-valley locked moire bands due to the intrinsic Ising spin-orbit coupling, homobilayer moire TMDs also possess either logarithmic or power-law divergent Van Hove singularities (VHS) near the Fermi surface, controllable by an external displacement field. The former and the latter are dubbed conventional and higher-order VHS, respectively. Here, we perform a perturbative renormalization group (RG) analysis to unbiasedly study the dominant instabilities in homobilayer TMDs for both the conventional and higher-order VHS cases. We find that the spin-valley locking largely alters the RG flows and leads to instabilities unexpected in the corresponding extensively-studied graphene-based moire systems, such as spin- and valley-polarized ferromagnetism and topological superconductivity with mixed parity. In particular, for the case with two higher-order VHS, we find a spin-valley-locking-driven metallic state with no symmetry breaking in the TMDs despite the diverging bare susceptibility. Our results show how the spin-valley locking significantly affects the RG analysis and demonstrate that moire TMDs are suitable platforms to realize various interaction-induced spin-valley locked phases, highlighting physics fundamentally different from the well-studied graphene-based moire systems.

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