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

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 non-linearity (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 non-linear 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.

12 pages, 5 figures

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Cited by in corpus (9)

• From Andreev to Majorana bound states in hybrid superconductor-semiconductor nanowires
• Physical mechanisms for zero-bias conductance peaks in Majorana nanowires
• Disorder-induced zero-bias peaks in Majorana nanowires
• Spin-Orbit Protection of Induced Superconductivity in Majorana Nanowires
• Quantized and unquantized zero-bias tunneling conductance peaks in Majorana nanowires: Conductance below and above $2e^2/h$
• Role of dephasing on the conductance signatures of Majorana zero modes
• Can non-local conductance spectra conclusively signal Majorana zero modes? -- Insights from von Neumann entropy
• Enhanced Majorana bound states in magnetic chains on superconducting topological insulator edges
• Rashba spin-orbit coupling and artificially engineered topological superconductors