Proximity-induced superconductivity in PbTe/Pb heterostructures from first principles

Abstract

Semiconductor-superconductor interfaces play a crucial role in various applications, including hybrid circuits, thermometry, devices (bolometers, electronic coolers), detectors for high-energy particle physics, and quantum computing as potential hosts of topologically protected zero-energy modes. In this work, we solve the Kohn-Sham density-functional theory and Bogoliubov–de Gennes equations to describe the normal and superconducting properties of a PbTe/Pb heterostructure. We compute the anomalous charge density in real space, estimating its decay length and showing that the pairing potential is anisotropic. We demonstrate that superconductivity in the PbTe/Pb interface is resilient against strain. In the normal state we find a large Schottky barrier across the interface, resulting in charge transfer from PbTe to Pb. We resolve a proximity-induced superconducting gap on the PbTe side, which originates from hybridization between the Pb and PbTe states near the Fermi energy, which occurs in a weak-coupling regime. On the Pb side, the superconducting gap appears partially “poisoned,” namely less sharp and less wide than bulk Pb. Our first-principles simulations provide a quantitative prediction on emergent structural, electronic (charge transfer, potential drops, band offset), and superconducting properties of the PbTe/Pb interface, namely key information for the design of devices where the PbTe/Pb interface plays a central role as, for instance, in core/shell PbTe/Pb nanowires.