Quantized zero-bias conductance plateau in semiconductor-superconductor heterostructures without topological Majorana zero modes

Recent observations of robust zero-bias quantized conductance plateaus of height 2 e²/h in quantum dot-semiconductor-superconductor nanowire heterostructures have been interpreted as clear evidence for the presence of non-Abelian topologically protected Majorana zero modes (MZMs), since other sources of low-energy conductance are believed to be unable to produce such quantized plateaus. Based on extensive numerical calculations, we show that, in fact, quantized conductance plateaus of height 2 e²/h can also arise as a result of partially separated Andreev bound states (ps-ABSs), in which the component Majorana bound states are somewhat shifted in space without being topological MZMs. As ps-ABSs can form rather generically in the topologically trivial phase, even in the absence of disorder, our results conclusively establish that the observation of quantized conductance plateaus of height 2 e²/h does not represent sufficient evidence for the existence of topologically protected MZMs localized at the opposite ends of a wire.