Non-Local Conductance in Three-Terminal Majorana Nanowires, Part 1 — Deterministic Control over Crossed Andreev Reflection Using Quantum Dots

The hallmark of proximity-induced superconductivity in a semiconducting system is the energy gap, resulting from the electron-hole correlations formed in the semiconductor through Andreev reflections. These correlations are also present above the gap, where the quasiparticle excitations have both an electron and a hole character. While conventional tunnel spectroscopy is only sensitive to the local density of states, non-local measurements are sensitive to the bulk properties of the proximitized system. We study the non-local conductance of an InSb nanowire coupled to superconducting Al, where the conductance is carried out through a quantum dot. By tuning the dot's potential and the applied bias, we deterministically control the non-local transport mechanism — crossed Andreev reflection or direct transport — and thus measure separately the electron and hole components of the quasiparticle wavefunction. We show that these two components are of similar magnitude, in full agreement with the BCS prediction.