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arXiv 2406.03530cond-mat.str-el
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转角双层MoTe$_2$中的分数量子陈绝缘体:复合费米子视角

Fractional Chern Insulators in Twisted Bilayer MoTe$_2$: A Composite Fermion Perspective

Tianhong Lu, Luiz H. Santos

AI总结:

本研究从复合费米子视角探究转角双层MoTe$_2$的晶格效应对拓扑相的影响,解释了实验观测到的多组分数填充下的分数量子陈绝缘体态,发现高阶范霍夫奇点等新现象,为过渡金属二硫化物莫尔系统的分数量子陈绝缘体研究提供框架。

摘要:

转角双层MoTe$_2$中分数量子陈绝缘体(FCI)的发现,引发了学界对无外磁场下分数拓扑物质的极大研究兴趣。与朗道能级的平坦色散不同,莫尔电子态会受到纳米尺度超晶格内晶格效应的影响。本研究探究了这些晶格效应对转角双层MoTe$_2$中拓扑相的影响,发现了一类具有阿贝尔任意子准粒子的分数量子陈绝缘体。借助复合费米子方法,我们识别出一系列分数量子陈绝缘体,其分数霍尔电导率为$σ_{xy} = \frac{C}{2C + 1} \frac{e^2}{h}$,与最上层莫尔价带的空穴部分填充因子$ν_{\text{h}}$相关。这些态源于复杂霍夫施塔特能谱中陈数为$C$的不可压缩复合费米子带。该方法解释了实验中观测到的、在分数填充因子$ν_{\text{h}} = 2/3$和$ν_{\text{h}} = 3/5$下霍尔电导率分别为$σ_{xy} = (2/3) e^2/h$和$σ_{xy} = (3/5) e^2/h$的分数量子陈绝缘体,还发现了其他分形分数量子陈绝缘体态。霍夫施塔特能谱揭示了有别于朗道能级的新现象,包括半填充时的高阶范霍夫奇点(HOVHS),可引发新型量子相变。本研究为理解过渡金属二硫化物莫尔系统中的分数量子陈绝缘体提供了全面框架,并阐明了拓扑量子临界性的相关机制。

英文摘要:

The discovery of Fractional Chern Insulators (FCIs) in twisted bilayer MoTe$_2$ has sparked significant interest in fractional topological matter without external magnetic fields. Unlike the flat dispersion of Landau levels, moiré electronic states are influenced by lattice effects within a nanometer-scale superlattice. This study examines the impact of these lattice effects on the topological phases in twisted bilayer MoTe$_2$, uncovering a family of FCIs with Abelian anyonic quasiparticles. Using a composite fermion approach, we identify a sequence of FCIs with fractional Hall conductivities $σ_{xy} = \frac{C}{2C + 1} \frac{e^2}{h}$ linked to partial filling $ν_{\,\text{h}}$ of holes of the topmost moiré valence band. These states emerge from incompressible composite fermion bands of Chern number $C$ within a complex Hofstadter spectrum. This approach explains FCIs with Hall conductivities $σ_{xy} = (2/3) e^2/h$ and $σ_{xy} = (3/5) e^2/h$ at fractional fillings $ν_{\,\text{h}} = 2/3$ and $ν_{\,\text{h}} = 3/5$ observed in experiments, and uncovers other fractal FCI states. The Hofstadter spectrum reveals new phenomena, distinct from Landau levels, including a higher-order Van Hove singularity (HOVHS) at half-filling, leading to novel quantum phase transitions. This work offers a comprehensive framework for understanding FCIs in transition metal dichalcogenide moiré systems and highlights mechanisms for topological quantum criticality.

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