Topologically trivial zero bias conductance peak in semiconductor Majorana wires from boundary effects

We show that a topologically trivial zero bias conductance peak (of height 4e^2/h) is produced in semiconductor-superconductor hybrid nanowires due to a suppressed pair potential and/or an excess Zeeman field at the ends of the heterostructure, both of which can occur in experiments. The zero bias peak (ZBP) (a) appears above a threshold parallel bulk Zeeman field, (b) is stable for a range of bulk field before splitting, (c) disappears with rotation of the bulk Zeeman field, and, (d) is robust to weak disorder fluctuations. The ZBPs from the nanowire ends are also expected to produce splitting oscillations with the applied field similar to those from Majorana fermions. We find that the only unambiguous way to distinguish these trivial ZBPs (of height 4e^2/h) from those arising from Majorana fermions (of height 2e^2/h) is by comparing the (zero temperature) peak height and/or through an interference experiment.