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Physical mechanisms for zero-bias conductance peaks in Majorana nanowires

Hai-Ning Pan, S. Das Sarma

Physical Review Research, 2019

200 citations

Abstract

Motivated by the need to understand and simulate the ubiquitous experimentally-observed zero-bias conductance peaks in superconductor-semiconductor hybrid structures, we theoretically investigate the tunneling conductance spectra in one-dimensional nanowires in proximity to superconductors in a systematic manner taking into account several different physical mechanisms producing zero-bias conductance peaks. The mechanisms we consider are the presence of quantum dots, inhomogeneous potential, random disorder in the chemical potential, random fluctuations in the superconducting gap, and in the effective $g$ factor with the self-energy renormalization induced by the parent superconductor in both short ($L\sim1~\mu$m) and long nanowires ($L\sim3~\mu$m). We classify all foregoing theoretical results for zero-bias conductance peaks into three types: the good, the bad, and the ugly, according to the physical mechanisms producing the zero-bias peaks and their topological properties. We find that, although the topological Majorana zero modes are immune to weak disorder, strong disorder (ugly) completely suppresses topological superconductivity and generically leads to trivial zero bias peaks. Compared qualitatively with the extensive existing experimental results in the superconductor-semiconductor nanowire structures, we conclude that most current experiments are likely exploring trivial zero-bias peaks in the ugly situation dominated by strong disorder. We also study the nonlocal…

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