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arXiv 1105.4867cond-mat.str-el
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分数阶陈式绝缘子

Fractional Chern Insulator

N. Regnault, B. Andrei Bernevig

摘要:

陈氏绝缘体是一种具有非零霍尔电导但保持晶格平移对称性的带状绝缘体。我们最终表明,部分填充的陈绝缘体在1/3填充表现出分数量子霍尔效应和排除电荷密度波状态,没有被排除在以前的研究。通过对角化这些绝缘体的平带极限中的Hubbard相互作用,我们表明:该系统是不可压缩的,有一个3重简并基态,其动量可以通过假设一个广义泡利原理计算,在3个连续轨道中不超过1个粒子。基态密度为常数,在动量空间中为1/3。系统的激发是分数统计粒子,其总计数与基于相同的广义泡利原理的Laughlin态中的准空穴的计数相匹配。态的纠缠谱具有明显的纠缠能隙,在热力学极限下纠缠能隙似乎是有限的。能隙以下能级的计数与Laughlin 1/3准空穴的计数相同。3个基态和激发态在磁通插入时都表现出光谱流。在绝缘体的平凡态中,上述所有性质都消失了--当单粒子哈密顿量从拓扑非平凡变为拓扑平凡时,多体能隙和纠缠能隙都在相变处闭合。这些事实清楚地表明,分数多体态在拓扑绝缘体中是可能的。

英文摘要:

Chern insulators are band insulators exhibiting a nonzero Hall conductance but preserving the lattice translational symmetry. We conclusively show that a partially filled Chern insulator at 1/3 filling exhibits a fractional quantum Hall effect and rule out charge-density wave states that have not been ruled out by previous studies. By diagonalizing the Hubbard interaction in the flat-band limit of these insulators, we show the following: The system is incompressible and has a 3-fold degenerate ground state whose momenta can be computed by postulating an generalized Pauli principle with no more than 1 particle in 3 consecutive orbitals. The ground state density is constant, and equal to 1/3 in momentum space. Excitations of the system are fractional statistics particles whose total counting matches that of quasiholes in the Laughlin state based on the same generalized Pauli principle. The entanglement spectrum of the state has a clear entanglement gap which seems to remain finite in the thermodynamic limit. The levels below the gap exhibit counting identical to that of Laughlin 1/3 quasiholes. Both the 3 ground states and excited states exhibit spectral flow upon flux insertion. All the properties above disappear in the trivial state of the insulator - both the many-body energy gap and the entanglement gap close at the phase transition when the single-particle Hamiltonian goes from topologically nontrivial to topologically trivial. These facts clearly show that fractional many-body states are possible in topological insulators.

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