Kavli Affiliate: Michael Wimmer
| First 5 Authors: Haining Pan, Chun-Xiao Liu, Michael Wimmer, Sankar Das Sarma,
| Summary:
Majorana zero modes can appear at the wire ends of a 1D topological
superconductor and manifest themselves as a quantized zero-bias conductance
peak in the tunneling spectroscopy of normal-superconductor junctions. However,
in superconductor-semiconductor hybrid nanowires, zero-bias conductance peaks
may arise owing to topologically trivial mechanisms as well, mimicking the
Majorana-induced topological peak in many aspects. In this work, we
systematically investigate the characteristics of zero-bias conductance peaks
for topological Majorana bound states, trivial quasi-Majorana bound states and
low-energy Andreev bound states arising from smooth potential variations, and
disorder-induced subgap bound states. Our focus is on the conductance peak
value (i.e., equal to, greater than, or less than $2e^2/h$), as well as the
robustness (plateau- or spike-like) against the tuning parameters (e.g., the
magnetic field and tunneling gate voltage) for zero-bias peaks arising from the
different mechanisms. We find that for Majoranas and quasi-Majoranas, the
zero-bias peak values are no more than $2e^2/h$, and a quantized conductance
plateau forms generically as a function of parameters. By contrast, for
conductance peaks due to low-energy Andreev bound states or disorder-induced
bound states, the peak values may exceed $2e^2/h$, and a conductance plateau is
rarely observed unless through careful postselection and fine-tuning. Our
findings should shed light on the interpretation of experimental measurements
on the tunneling spectroscopy of normal-superconductor junctions of hybrid
Majorana nanowires.
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