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Disorder-induced zero-bias peaks in Majorana nanowires

TitleDisorder-induced zero-bias peaks in Majorana nanowires
Publication TypeJournal Article
Year of Publication2021
AuthorsS. Das Sarma, and H. Pan
JournalPhys. Rev. B
Date PublishedMAY 28
Type of ArticleArticle

Focusing specifically on the recently retracted work by Zhang et al. {[}H. Zhang et al., Nature (London) 556, 74 (2018); Retraction, Nature (London) 591, E30 (2021)] and the related recently available correctly analyzed data from this Delft experiment (H. Zhang et al., arXiv:2101.11456), 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 similar to 2e(2)/h in the theory, closely mimicking the data. Thus, although the corrected Delft data are by far the best tunnel spectroscopy results available in the literature, manifesting large and sharp zero-bias peaks rising above the background with an impressive hard superconducting gap, our theory shows that the most natural explanation for these zero-bias peaks is that they are disorder induced and not topological Majorana modes. It is possible to misinterpret such disorder-induced zero-bias trivial peaks as the apparent Majorana quantization, as was originally done arising from confirmation bias. One characteristic of the disorder-induced trivial peaks is that they manifest little stability as a function of Zeeman field, chemical potential, 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 {[}P. Yu et al., Nat. Phys. 17, 482 (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 conductance values similar to 2e(2)/h in a dirty system manifesting very soft superconducting gap with substantial in-gap conduction, as were already reported by several groups almost 10 years ago. Removing disorder and producing cleaner samples through materials quality improvement and better fabrication is the only way for future progress in this field.