Hybrid superconductor-semiconductor devices are currently one of the most promising platforms for realizing Majorana zero modes. In this seminar I will address the role of band bending and superconductor-semiconductor hybridization in such devices by analyzing a gated Al-InAs planar interface. The problem is mainly attacked using a self-consistent Schrödinger-Poisson (SP) approach. Further insight is obtained via alternative approximate methods, i.e. the Thomas-Fermi-Poisson formalism and the analytical non self-consistent solution of the SP equations.

The three methods corroborate that the band bending leads to an interface quantum well, which localizes the charge in the system near the superconductor-semiconductor interface. Analyzing the obtained band structure reveals that achieving a high degree of hybridization requires a fine balance of the Al width, the gate voltage and the difference between the Al Fermi energy and the InAs electron affinity. To shed light on the interdependence of these factors I will provide approximate analytical expressions for the degree of hybridization, which can be used as a guide for the optimal design of future devices. Finally, I will comment on the consequences of these findings for the realization of Majorana zero modes in nanowires.

Reference: A. E. G. Mikkelsen, P. Kotetes, P. Krogstrup, and K. Flensberg, arXiv:1801.03439.

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