Crossover between trivial zero modes in Majorana nanowires
Crossover between trivial zero modes in Majorana nanowires
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DOI：
10.1103/physrevb.104.054510
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发表时间：
2021-02
影响因子：
3.7
通讯作者：
Haining Pan;S. Das Sarma
中科院分区：
文献类型：
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作者：
Haining Pan;S. Das Sarma
我们认为超导体-半导体纳米线混合马约拉纳平台（“马约拉纳纳米线”）中存在的确定性空间缓慢变化的不均匀化学势和随机的空间淬灭的潜在障碍，这两者都是已知的产生非拓扑几乎零能量模式模仿理论预测的拓扑马约拉纳零模式。我们研究了这些机制之间的交叉计算隧道电导，而不同的非均匀电位和随机无序之间的相对强度在一个受控的方式。我们发现，整个交叉区域表现出丰富的平凡零模式，其中许多显示出明显的“量化“的零偏压电导峰在2e^2/h $，偶尔的无序主导的峰超过2e^2/h $。我们提出了动画的模拟交叉行为，并讨论了实验的影响。此外，为了模拟实验纳米线中的实际无序，我们还深入研究了由随机单个静态杂质沿着线引起的无序的情况，并考虑与这种杂质效应相关的交叉。我们的研究结果，定性与现有的马约拉纳纳米线的实验结果相比，表明随机无序在实验中的主导作用。事实证明，所有三种机制都可能在隧道电导中产生微不足道的零偏置峰值，并且这些物理机制之间的交叉（即，当系统中存在一种以上的机制时）是平滑和连续的，使得仅通过零偏压电导峰值的偶然检查难以先验地推断出哪种机制在特定样品中占主导地位。
We consider the superconductor-semiconductor nanowire hybrid Majorana platform ("Majorana nanowire") in the presence of a deterministic spatially slowly varying inhomogeneous chemical potential and a random spatial quenched potential disorder, both of which are known to produce nontopological almost-zero-energy modes mimicking the theoretically predicted topological Majorana zero modes. We study the crossover among these mechanisms by calculating the tunnel conductance while varying the relative strength between inhomogeneous potential and random disorder in a controlled manner. We find that the entire crossover region manifests abundant trivial zero modes, many of which showing the apparent"quantization"of the zero-bias conductance peak at $ 2e^2/h $, with occasional disorder-dominated peaks exceeding $ 2e^2/h $. We present animations of the simulated crossover behavior and discuss experimental implications. Additionally, in order to simulate the realistic disorder in experimental nanowires, we also study in depth the case of disorder arising from random individual static impurities along the wire, and consider crossover associated with such impurity effects. Our results, when compared qualitatively with existing Majorana nanowire experimental results, indicate the dominant role of random disorder in the experiments. It turns out that all three mechanisms may produce trivial zero-bias peaks in the tunnel conductance, and the crossover among these physical mechanisms (i.e., when more than one mechanism is present in the system) is smooth and continuous, making it difficult a priori to conclude which mechanism is dominant in a particular sample just by a casual inspection of the zero-bias conductance peaks.