Majorana conductance quantization in the presence of momentum relaxation processes

Hybrid systems with proximity-induced superconductivity in semiconductor nanowires with spin-orbit coupling in a Zeeman field are a promising platform for hosting Majorana bound states (MBSs). In this work, we examine whether the quantized zero-bias conductance peak is robust enough to dephasing and momentum relaxation to remain a tell-tale signature of MBSs. We employ the Keldysh non-equilibrium Green’s function (NEGF) formalism to model quantum transport through the Majorana nanowire in an NSN setup. As expected, in the clean and phase-coherent limit, MBSs give rise to a quantized zero-bias peak (ZBP) in differential conductance, dominated by the local Andreev reflection. However, in the presence of phase and momentum relaxing interactions [1], we show that this ZBP signature is suppressed and does not remain quantized. For nanowires with short phase coherence lengths, such processes can render the ZBP indistinguishable from noise even in the presence of topological MBSs in the local density of states. Thus, we suggest that in Majorana nanowire experiments with scattering and relaxation effects, the absence of a quantized ZBP in conductance measurements does not necessarily preclude the existence of Majorana states.
[1] P. Sriram et. al., Phys. Rev. B, 100, 155431 (2019)