Crossover between trivial zero modes in Majorana nanowires

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.

Automated summary

The study explores the properties of the superconductor-semiconductor nanowire hybrid Majorana platform in the presence of a deterministic slowly varying inhomogeneous chemical potential and a random quenched potential disorder. By calculating the tunnel conductance, the research examines the crossover among different mechanisms, with findings indicating the dominant role of random disorder in experiments.