论文标题
量子厅旋转液体及其在Moiré系统中的实现
Quantum Hall spin liquids and their possible realization in moiré systems
论文作者
论文摘要
最近，Chern Number $ C = 1 $和$ C = 2 $的Chern绝缘子在两个Moire石墨烯系统中观察到了零（或很小）的磁场：扭曲的双层石墨烯和ABC三层石墨烯，均与六边形的硼龙 - 荷兰（H-BN）substrate对齐。这些奇特绝缘子状态由于这些系统的Chern带中的许多身体效应而出现，当它们部分填充到总整数填充$ν_t= 1,3 $时（包括旋转和山谷的自由度）。一个简单的可能解释来自Hartree-fock平均场理论，该理论预测了零带宽极限的山谷和自旋极化，类似于Landau水平中的“量子霍尔铁磁性”。尽管现有实验暗示了山谷极化，但自旋程度的命运目前尚不清楚。在本文中，我们提出了替代山谷极化（但不是自旋极化）的候选，以观察到的QAH效应。对于填充$ν_t= 1 $的山谷极化的拼写串带，我们描述了一类奇特的Chern绝缘体阶段，通过自旋电荷分离：电荷位于常规的Chern绝缘体相，带有量化的霍尔电导率，而自旋形成无序的旋转液相则具有分数化，我们将量子量化量子霍尔自旋液体。我们构建了一个简单的$ z_2 $量子霍尔旋转液体的简单类，作为熟悉的$ z_2 $旋转液体的类似物，通过从奴隶费米恩·舒林 - 舒恩·波森·帕顿理论。从$ Z_2 $量子霍尔自旋液体中的Spinon凝结会导致量子厅抗铁磁铁，这是另一个实验观察到的Chern绝缘子的另一个，不太异国情调的候选者。我们提供了几项实验建议，以探测量子霍尔自旋液体和量子霍尔抗铁磁相。
Recently Chern insulators with Chern number $C=1$ and $C=2$ in zero (or very small) magnetic field have been observed in two moire graphene systems: twisted bilayer graphene and ABC trilayer graphene, both aligned with a hexagonal Boron-Nitride (h-BN) substrate. These Chern insulator states arise due to many body effects in the Chern bands of these systems when they are partially filled to a total integer filling $ν_T = 1,3$ (including spin and valley degrees of freedom). A simple possible explanation is from Hartree-Fock mean field theory which predicts valley and spin polarization in the zero bandwidth limit, similar to the "quantum Hall ferromagnetism" in Landau levels. Though valley polarization is implied by the existing experiments, the fate of the spin degree of freedom is not presently clear. In this paper we propose alternative valley polarized - but not spin polarized - candidates for the observed QAH effect. For a valley polarized spinful Chern band at filling $ν_T=1$, we describe a class of exotic Chern insulator phases through spin-charge separation: charge is in a conventional Chern insulator phase with quantized Hall conductivity, while the spin forms disordered spin liquid phase with fractionalization, which we dub quantum Hall spin liquids. We construct a simple class of $Z_2$ quantum Hall spin liquid as analogs of the familiar $Z_2$ spin liquid through slave fermion-schwinger boson parton theory. Condensation of the spinon from the $Z_2$ quantum Hall spin liquid can lead to a quantum Hall antiferromagnet which is yet another, less exotic, candidate for the experimentally observed Chern insulator. We offer several experimental proposals to probe the quantum Hall spin liquid and the quantum Hall anti-ferromagnetic phases.
