Kavli Affiliate: Michael Wimmer
| First 5 Authors: Sebastiaan L. D. ten Haaf, Yining Zhang, Qingzhen Wang, Alberto Bordin, Chun-Xiao Liu
| Summary:
A chain of quantum dots (QDs) in semiconductor-superconductor hybrid systems
can form an artificial Kitaev chain hosting Majorana bound states (MBSs). These
zero-energy states are expected to be localised on the edges of the chain, at
the outermost QDs. The remaining QDs, comprising the bulk, are predicted to
host an excitation gap that protects the MBSs at the edges from local on-site
perturbations. Here we demonstrate this connection between the bulk and edges
in a minimal system, by engineering a three-site Kitaev chain in a
two-dimensional electron gas. Through direct tunneling spectroscopy on each
site, we show that the appearance of stable zero-bias conductance peaks at the
outer QDs is correlated with the presence of an excitation gap in the middle
QD. Furthermore, we show that this gap can be controlled by applying a
superconducting phase difference between the two hybrid segments and that the
MBSs are robust only when the excitation gap is present. We find a close
agreement between experiments and the original Kitaev model, thus confirming
key predictions for MBSs in a three-site chain.
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