Non-Majorana states yield nearly-quantized conductance in proximatized nanowires

Semiconductor nanowires with proximity-induced superconductivity are leading contenders for manifesting Majorana fermions in condensed matter. However, unambiguous detection of these quasiparticles is controversial, and one proposed method is to show that the peak in the conductance at zero applied bias is quantized to the value of 2e^2/h. Here, we fabricate devices that feature tunnel probes on both ends of a nanowire and observe zero-bias peaks that are close to the quantized value. These peaks evolve with the tunnel barrier strength and magnetic field in a way that is consistent with Majorana zero modes. However, we only find nearly-quantized zero-bias peaks localized to one end of the nanowire, while conductance dips are observed for the same parameters at the other end. Yet if peaks come from Majorana modes they should be observed at both ends simultaneously. These results imply either a topological segment shorter than the superconducting segment which is 400 nm, or a non-Majorana origin of the observed quantized zero-bias peaks. We also lay out procedures for assessing the nonlocality of subgap wave functions and provide a classification of nanowire bound states based on their localization.