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arXiv 2501.09059cond-mat.str-elcond-mat.mes-hall
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变分波函数用于分数拓扑绝缘体

Variational wavefunctions for fractional topological insulators

Institute for Theoretical Physics, ETH Zürich(苏黎世联邦理工学院理论物理研究所);Department of Physics, University of Zürich(苏黎世大学物理系)

Glenn Wagner, Titus Neupert

AI总结:

研究揭示了在反向陈数情况下,变分波函数无法有效建模,强调需抑制短程互旋库仑排斥以实现分数拓扑绝缘体。

摘要:

扭曲过渡金属二硫化物(TMDs)具有相反陈数的能带,可能支持分数拓扑绝缘体状态。在多组分量子霍尔系统中,当自旋具有相等陈数时,拓扑液体状态可通过试波函数如Halperin (lmn)波函数建模。这些波函数是某些短程(伪势能)哈密顿量的精确零能态。然而,我们显示在自旋陈数相反的情况下,此类构造失效,因为相反陈数的电子无法避免彼此。这突显了抑制短程互旋库仑排斥以在扭曲TMDs中实现分数拓扑绝缘体的重要性。我们引入了一种试波函数,用于填充因子ν=1/3+1/3的相反陈数朗德能级,通过复合费米子配对,并显示其在短程库仑排斥充分软化时与精确对角化基态有良好重叠。

英文摘要:

Twisted transition metal dichalcogenides (TMDs) host bands with opposite Chern number for the two spin species and could thus be host for fractional topological insulator states. In multicomponent quantum Hall systems, where the spins have equal Chern number, the resulting topological liquid states can be well modeled by trial wavefunctions such as the Halperin $(lmn)$ wavefunctions. These wavefunctions are exact zero energy states of certain short-range (pseudopotential) Hamiltonians. However, we show that such a construction fails in the case where the Chern numbers of the two spins are opposite, since the electrons with opposite Chern number cannot avoid one another. This underlines the importance of suppressing the short-range interspin Coulomb repulsion in order to realize fractional topological insulators in twisted TMDs. We introduce a trial wavefunction for the opposite Chern number Landau levels for filling factor $ν=\frac{1}{3}+\frac{1}{3}$ in terms of pairing of composite fermions and show that it has good overlaps with the exact diagonalization ground state when the short-range Coulomb repulsion is sufficiently softened.

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