Department of Physics, College of William and Mary, Williamsburg, Virginia 23187, USA.
Phys Rev Lett. 2013 Aug 23;111(8):086804. doi: 10.1103/PhysRevLett.111.086804. Epub 2013 Aug 22.
We study the "hybrid" heterostructure formed by one sheet of single-layer graphene (SLG) and one sheet of bilayer graphene (BLG) separated by a thin film of dielectric material. In general, it is expected that interlayer interactions can drive the system to a spontaneously broken-symmetry state characterized by interlayer phase coherence. The peculiarity of the SLG-BLG heterostructure is that the electrons in the two layers have different chiralities. We find that this difference causes the spontaneously broken-symmetry state to be N-fold degenerate. Moreover, we find that some of the degenerate states are chiral superfluid states, topologically distinct from the usual layer ferromagnetism. The chiral nature of the ground state opens the possibility to realize protected midgap states. The N-fold degeneracy of the ground state makes the physics of SLG-BLG hybrid systems analogous to the physics of 3He, in particular given the recent discovery of chiral superfluid states in this system.
我们研究了由单层石墨烯 (SLG) 和双层石墨烯 (BLG) 通过薄介电层形成的“混合”异质结构。一般来说，人们期望层间相互作用可以驱动系统进入由层间相位相干性表征的自发对称破缺状态。SLG-BLG 异质结构的特点是两层中的电子具有不同的手性。我们发现这种差异导致自发对称破缺状态是 N 重简并的。此外，我们发现一些简并态是手性超流态，与通常的层铁磁态拓扑不同。基态的手性性质为实现受保护的带隙态提供了可能性。基态的 N 重简并使 SLG-BLG 混合系统的物理性质类似于 3He 的物理性质，特别是考虑到最近在该系统中发现了手性超流态。
