Center for Materials Theory, Rutgers University, Piscataway, New Jersey 08854, USA.
Phys Rev Lett. 2012 Jul 27;109(4):046803. doi: 10.1103/PhysRevLett.109.046803.
Motivated to understand the nature of the strongly insulating ν=0 quantum Hall state in bilayer graphene, we develop the theory of the state in the framework of quantum Hall ferromagnetism. The generic phase diagram, obtained in the presence of the isospin anisotropy, perpendicular electric field, and Zeeman effect, consists of the spin-polarized ferromagnetic (F), canted antiferromagnetic (CAF), and partially (PLP) and fully (FLP) layer-polarized phases. We address the edge transport properties of the phases. Comparing our findings with the recent data on suspended dual-gated devices, we conclude that the insulating ν=0 state realized in bilayer graphene at lower electric field is the CAF phase. We also predict a continuous and a sharp insulator-metal phase transition upon tilting the magnetic field from the insulating CAF and FLP phases, respectively, to the F phase with metallic edge conductance 2e(2)/h, which could be within the reach of available fields and could allow one to identify and distinguish the phases experimentally.
为了深入理解双层石墨烯中具有强绝缘性质的ν=0 量子霍尔态的本质，我们在量子霍尔亚铁磁体的理论框架下发展了该态的理论。在存在同位旋各向异性、垂直电场和塞曼效应的情况下，得到了一般的相图，它由自旋极化铁磁（F）、倾斜反铁磁（CAF）以及部分（PLP）和完全（FLP）层极化相组成。我们研究了这些相的边缘输运性质。将我们的发现与最近关于悬浮双栅器件的实验数据进行比较后，我们得出结论，在较低电场下在双层石墨烯中实现的绝缘ν=0 态是 CAF 相。我们还预测，在磁场从绝缘 CAF 和 FLP 相倾斜到具有金属边缘电导 2e(2)/h 的 F 相时，会发生连续和尖锐的绝缘-金属相变，这可能在现有磁场的范围内，并允许人们在实验中识别和区分这些相。
