Artificial Kitaev chains in Two-Dimensional Electron Gases

Abstract

Majorana zero modes are neutral excitations—equal superpositions of an electron and a hole in a superconductor.
Their non-Abelian statistics make them promising building blocks for topological quantum computation.
In semiconductor–superconductor hybrids, however, disorder and trivial bound states often obscure Majorana signatures,
making conclusive evidence elusive. This challenge motivates new device concepts or alternative engineering strategies.

In this thesis, we bridge a traditional and a new bottom-up routes to realize Majorana modes in two-dimensional electron gases (2DEGs), and develop a fabrication workflow for complex device geometries.
We first implement the Lutchyn–Oreg approach in gate-defined wires and develop multiprobe spectroscopy with multiple tunnel probes to assess spatial uniformity.
These measurements reveal subgap states that are often uncorrelated between neighboring probes, though some devices show striking probe-to-probe correlations.
These observations indicate that disorder and inhomogeneity can drive inconsistent behavior across similar devices, limiting prospects for a robust global topological phase.

This motivates an alternative pathway: constructing artificial Kitaev chains using quantum dots.In the second experiment, we establish controllable elastic cotunneling and crossed Andreev reflection, via gate-tunable Andreev bound states that couple the dots.
We demonstrate Cooper pair splitting and at finite magnetic field, we are able to resolve substantial triplet correlations due to the strong spin orbit coupling in the 2DEGs.

In the third experiment, we push the system into the strong-coupling regime and realize a two-site Kitaev chain.
By tuning dot levels, the ABS energy, and the in-plane magnetic-field orientation, we reach “sweet spots” with correlated zero-bias peaks that are robust to local perturbations.
Notably, these peaks can already appear at zero Zeeman energy—consistent with a spinful two-site chain.
Comparing the full excitation spectrum to numerical simulations allows us to estimate the Majorana polarization in representative settings.

We conclude this thesis by outlining next steps: extending the Kitaev chain and implementing parity readout to enable manipulation and measurement of multiple MBSs.
We also assess alternative material platforms for proof-of-principle Kitaev-chain devices.