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Curvature of gap closing features and the extraction of Majorana nanowire parameters

TitleCurvature of gap closing features and the extraction of Majorana nanowire parameters
Publication TypeJournal Article
Year of Publication2019
AuthorsH. Pan, J. D. Sau, T. D. Stanescu, and S. Das Sarma
JournalPhys. Rev. B
Volume99
Pagination054507
Date PublishedFEB 15
Type of ArticleArticle
ISSN2469-9950
Abstract

Recent tunneling conductance measurements of Majorana nanowires show a strong variation in the magnetic-field dependence of the superconducting gap among different devices. Here, we theoretically study the magnetic field dependence of the gap closing feature and establish that the degree of convexity (or concavity) of the gap closing as a function of Zeeman field can provide critical constraints on the underlying microscopic parameters of the semiconductor-superconductor hybrid system model. Specifically, we show that the gap closing feature is entirely concave only for strong spin-orbit coupling strength relative to the chemical potential. Additionally, the nonlinearity (i.e., concavity or convexity) of the gap closing as a function of magnetic field complicates the simple assignment of a constant effective g-factor to the states in the Majorana nanowire. We develop a procedure to estimate the effective g-factor from recent experimental data that accounts for the nonlinear gap closing, resulting from the interplay between chemical potential and spin-orbit coupling. Thus, measurements of the magnetic field dependence of the gap closure on the trivial side of the topological quantum phase transition can provide useful information on parameters that are critical to the theoretical modeling of Majorana nanowires.

DOI10.1103/PhysRevB.99.054507