Kitaev model with quantum dot chains in semiconductor nanowires
We experimentally explore whether chains of quantum dots in semiconductor nanowires can be used to emulate important one-dimensional Hamiltonians such as the topological p-wave superconductor. First, we have realized a building block of the Kitaev model by establishing a double quantum dot with superconducting contacts in an InSb nanowire. We demonstrated that Andreev bound states in each dot hybridize to form the double-dot Andreev molecular states. We showed the parity and the spin structure of Andreev molecular levels. Understanding Andreev molecules is a key step towards building longer chains which are predicted to generate Majorana bound states at the end sites.
Next, we have implemented a triple quantum dot chain in an InSb nanowire where each dot is tuned to be strongly coupled to a separate NbTiN superconducting lead. We have studied transport through Andreev bound states on individual dots, dot pairs and through the entire triple dot chain. We explore the influence of Coulomb energy on the Andreev spectra of the chain. We use magnetic fields parallel to the nanowire axis to study the field dependence of the triple dot Andreev bound states. We observe zero bias conductance peaks that appear at finite applied magnetic fields, as well as split peaks. We explore these conductance resonances in the context of Majorana bound states, as well as considering supercurrents and trivial Andreev bound states.