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) coupled via semiconductor-superconductor hybrid
regions 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. In this work, 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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