Signatures of Majorana Fermions in Hybrid Superconductor-Semiconductor Nanowire Devices

摘要

Majorana fermions are exotic elementary particles predicted in 1937 by Ettore Majorana. Although heavily searched for, they have never been found in nature up to date. In the past decades, with the progress in theory, theoretical physicists predicted that Majorana fermions might emerge in certain exotic classes of condensed matter systems, where they show up as ’quasi-particles’. Due to their special statistics properties, Majorana fermions in condensed matter are expected to be applied as building blocks of topological quantum computers. This thesis is about creating and detecting Majorana fermions in one of these special systems, which consists of a semiconducting Indium Antimonide nano- wire in contact with a superconductor (Niobium Titanium Nitride). Majorana fermions are expected to appear at very low temperatures below 100 milliKelvin and in the presence of a strong magnetic field. After successfully engineering the device, in a first series of experiments a striking feature has been found indicating the existence of Majorana fermions. Furthermore, two important side tracks related to the main research topic are studied. Firstly, spin-orbit interaction in quantum dots gives a first indication of the strength of spin-orbit interaction in the Indium Antimonide nanowire is explored. Secondly, Josephson effect in Indium Antimonidenanowire based Josephson junctions are measured, shown new types of behaviours in magnetic field, highly relevant to both Majorana fermion research in nanowires, and the research on the Josephson effect in general.