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arXiv 1207.2133cond-mat.mes-hall
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分数填充Chern带的Hamilton理论

Hamiltonian theory of fractionally filled Chern bands

Ganpathy Murthy, R. Shankar

摘要:

有令人信服的数值证据表明,分数填充的陈氏带(FCB)中出现了分数量子霍尔(HHH)类基态。在这里,我们表明,复合费米子(CF)的哈密顿理论可以作为有用的描述FCB,因为它是在描述的连续介质中的ECOHE。我们能够引入CF到FCB问题,即使没有外部磁场通过以下两个阶段的过程。首先,我们构建一个代数精确映射,它表示的电子密度投影到陈带,$ρ_{\tiny FCB}$,作为一个总和的Girvin-MacDonald-Platzman密度算子,$ρ_{\tiny GMP}$,服从磁平移代数。接下来,根据我们的哈密顿处理的问题,我们重写GMP运营商的CF变量,重现相同的代数。这自然会产生一个独特的Hartree-Fock基态的CF,它可以被用来作为一个跳板计算间隙,响应函数,温度依赖的现象,和无序的影响。我们给出了两个具体的例子,其中之一是没有类似的连续体中的$ν= {1 \over 5}$和$σ_{xy}={2\over 5}$。我们的方法可以很容易地扩展到分数填充,强相互作用的二维时间反演不变的拓扑绝缘体。

英文摘要:

There is convincing numerical evidence that fractional quantum Hall (FQH)-like ground states arise in fractionally filled Chern bands (FCB). Here we show that the Hamiltonian theory of Composite Fermions (CF) can be as useful in describing the FCB as it was in describing the FQHE in the continuum. We are able to introduce CFs into the FCB problem even though there is no external magnetic field by following a two-stage process. First we construct an algebraically exact mapping which expresses the electron density projected to the Chern band, $ρ_{\tiny FCB}$, as a sum of Girvin-MacDonald-Platzman density operators, $ρ_{\tiny GMP}$, that obey the Magnetic Translation Algebra. Next, following our Hamiltonian treatment of the FQH problem, we rewrite the GMP operators in terms of CF variables which reproduce the same algebra. This naturally produces a unique Hartree-Fock ground state for the CFs, which can be used as a springboard for computing gaps, response functions, temperature-dependent phenomena, and the influence of disorder. We give two concrete examples, one of which has no analog in the continuum FQHE with $ν= {1 \over 5}$ and $σ_{xy}={2\over 5}$. Our approach can be easily extended to fractionally filled, strongly interacting two-dimensional time-reversal-invariant topological insulators.

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