论文标题
河谷的磁性，nematicity和密度波顺序在扭曲的双层石墨烯中
Valley magnetism, nematicity, and density wave orders in twisted bilayer graphene
论文作者
论文摘要
我们分析了扭曲的双层石墨烯中的密度波和Pomeranchuk订单。这补充了我们对配对不稳定性的早期分析。我们假设传导或价带的一半填充，费米水平接近范霍夫点，在该点的密度分散，并在具有两个山谷自由度的斑块模型中研究粒子孔通道中的潜在不稳定性。扭曲的双层石墨烯的六角形对称性允许六个或十二个范霍夫点。我们考虑这两个情况，并找到相同的两个领先候选粒子序列。一个是山谷中具有铁磁性的su（2）旋转状态。山地界面的跳线会引起山谷之间的反铁磁性。在强耦合方法中也获得了相同的状态，表明该顺序是强大的。另一个是一个混合状态，带有$ 120^\ circ $复杂的旋转顺序和正交复杂的费用订单。此外，我们发现在列神经通道中的较弱但仍然有吸引力的相互作用，并讨论了列前顺序的类型。
We analyze density-wave and Pomeranchuk orders in twisted bilayer graphene. This compliments our earlier analysis of the pairing instabilities. We assume that near half-filling of either conduction or valence band, the Fermi level is close to Van Hove points, where the density of states diverges, and study potential instabilities in the particle-hole channel within a patch model with two valley degrees of freedom. The hexagonal symmetry of twisted bilayer graphene allows for either six or twelve Van Hove points. We consider both cases and find the same two leading candidates for particle-hole order. One is an SU(2)-breaking spin state with ferromagnetism within a valley. A subleading inter-valley hopping induces antiferromagnetism between the valleys. The same state has also been obtained in strong coupling approaches, indicating that this order is robust. The other is a mixed state with $120^\circ$ complex spin order and orthogonal complex charge order. In addition, we find a weaker, but still attractive interaction in nematic channels, and discuss the type of a nematic order.
