Multi-band Physics in Inhomogeneous Majorana Nanowires

Semiconductor nanowires proximity coupled to superconductors are a promising platform to detect and manipulate Majorana zero energy modes. Single band models are used ubiquitously throughout the literature to describe these systems. In practice, however, it is quite likely that multiple confinement bands determine the properties of these devices, which can lead to new features not predicted by the single band models. We consider different types of inhomogeneity, such as a quantum dot defined by a region of the nanowire not covered by the superconductor. As previously shown, the dot region can give rise to Andreev bound states that mimic some of the signatures of Majorana zero modes. We find an increased pinning of Andreev bound states to zero energy within the multi-band model due to strong inter-band coupling induced by an inhomogeneous electrostatic potential. Understanding in detail the multi-band effects are important for the practical realization of Majorana zero modes in semiconductor-superconductor nanowire devices.