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arXiv 2001.02245cond-mat.mes-hall
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分数量子Hall边的拓扑超导电性和顺费子零模特征

Signatures of Topological Superconductivity and Parafermion Zero Modes in Fractional Quantum Hall Edges

Noam Schiller, Eyal Cornfeld, Erez Berg, Yuval Oreg

摘要:

仿费米子零模是奇异的涌现激发,可以被认为是马约拉纳费米子的$\mathbb{Z}_n$推广。它们存在于分数量子霍尔-超导体混合系统等中,可以作为容错拓扑量子计算的潜在构建模块。我们提出了一个系统,揭示了噪音和电流签名指示parafermion零模式。该系统由填充因子为$ν= 1/m$(对于奇数$m$)的分数量子霍尔体的边缘激发(“准粒子”)入射到超导体的界面上,并且存在背散射。使用微扰计算,我们推导出的电流传播远离这个结构,和它相应的噪声关联函数。重整化群分析揭示了从UV固定点的完美正常反射到IR固定点的完美Andreev反射的流动。这些固定点附近的微分电导的幂律依赖性由$m$确定。我们发现,在这两个极限的行为是物理上可区分的,而接近完美的Andreev反射,系统偏离平衡通过隧道的两个边缘之间的库珀对,接近完美的正常反射,这是通过隧道的一个单一的准粒子到一个紧急的parafermion零模式在超导体界面。这些结果得到了精确解的证实。

英文摘要:

Parafermion zero modes are exotic emergent excitations that can be considered as $\mathbb{Z}_n$ generalizations of Majorana fermions. Present in fractional quantum Hall-superconductor hybrid systems, among others, they can serve as potential building blocks in fault-tolerant topological quantum computing. We propose a system that reveals noise and current signatures indicative of parafermion zero modes. The system is comprised of the edge excitations ("quasi-particles") of a fractional quantum Hall bulk at filling factor $ν= 1/m$ (for odd integer $m$) incident upon the interface of a superconductor, and in the presence of back-scattering. Using perturbative calculations, we derive the current that propagates away from this structure, and its corresponding noise correlation function. Renormalization group analysis reveals a flow from a UV fixed point of perfect normal reflection towards an IR fixed point of perfect Andreev reflection. The power law dependence of the differential conductance near these fixed points is determined by $m$. We find that behavior at these two limits is physically distinguishable; whereas near perfect Andreev reflection, the system deviates from equilibrium via tunneling of Cooper pairs between the two edges, near perfect Normal reflection this is done via tunneling of a single quasi-particle to an emergent parafermion zero mode at the superconductor interface. These results are fortified by an exact solution.

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