Disorder-induced zero-bias peaks in Majorana nanowires

Focusing specifically on the recently retracted Nature 2018 Zhang et al. work [Zhang et al., Nature (2021)] and the related recently available correctly analyzed data from this Delft experiment [Zhang et al., arXiv:2101.11456 (2021)], we discuss the general problem of confirmation bias in experiments verifying various theoretical topological quantization predictions. We show that the Delft Majorana experiment is most likely dominated by disorder, which produces trivial (but quite sharp and large) zero-bias Andreev tunneling peaks with large conductance $ \sim 2e^2/h $ in the theory, closely mimicking the data. It is possible to misinterpret such disorder-induced zero-bias trivial peaks as the apparent Majorana quantization, as was originally done in 2018 arising from confirmation bias. One characteristic of the disorder-induced trivial peaks is that they manifest little stability as a function of Zeeman field and tunnel barrier, distinguishing their trivial behavior from the expected topological robustness of non-Abelian Majorana zero modes. We also analyze a more recent nanowire experiment [Yu et al., Nature Physics (2021)] which is known to have a huge amount of disorder, showing that such highly disordered nanowires may produce very small above-background trivial peaks with values $ \sim 2e^2/h $.