Nonlocal transport signatures of Andreev bound states

Andreas Pöschl

Published 2022-12-22Version 1

In this PhD thesis, quantum devices based on molecular-beam epitaxy grown InAs semiconductor with an in-situ grown epitaxial Al film were investigated. Novel device geometries were realized that allow for the study of bound states that emerge at low temperatures in semiconducting nanowires due to the presence of spin-orbit coupling, Zeeman effect, and superconducting proximity effect. Experiments utilizing either gate-defined nanowires in two-dimensional heterostructures or vapor-liquid-solid grown nanowires with a full-shell of Al are presented. Devices and experimental methods were developed that allow for tunneling spectroscopy at multiple locations of a nanowire. Results of nonlocal conductance transport measurements of Andreev bound states are discussed. Due to their extended wavefunction, bound states that are locally hybridized with a quantum dot show characteristic signatures in tunneling spectroscopy at neighboring measurement locations. If the distance between neighboring tunneling measurement locations is larger than 0.8 $\mathrm{\mu m}$ no signatures of extended bound states was observed.