Andreev interference in the surface accumulation layer of half-shell InAsSb/Al hybrid nanowires

Abstract

Understanding the spatial distribution of charge carriers in III-V nanowires proximity coupled to superconductors is important for the design and interpretation of experiments based on hybrid quantum devices. In this letter, the gate-dependent surface accumulation layer of InAsSb/Al nanowires was studied by means of Andreev interference in a parallel magnetic field. Both uniform hybrid nanowires and devices featuring a short Josephson junction fabricated by shadow lithography, exhibited periodic modulation of the switching current. The period corresponds to a flux quantum through the nanowire diameter and is consistent with Andreev bound states occupying a cylindrical surface accumulation layer. The spatial distribution was tunable by a gate potential as expected from electrostatic models.

Quasiparticle trapping by orbital effect in a hybrid superconducting-semiconducting circuit

“…This observation is in agreement with the density of states being confined towards the superconducting shell, improving the induced superconducting gap. We observe a local minimum around B = 0.3 T, consistent with the flux induced interference effects as explained in the main text, and also reported by [26,30].…”

“…When the JJ is protected by the gate-controlled QP filters, we find peaks of enhanced charge-parity lifetimes induced by the magnetic field and centered around odd multiples of B ∼ 280 mT. We attribute these enhancements to the formation of quasiparticle traps in the ungated NW segments as a result of a local suppression of the induced gap by the orbital effect [26][27][28][29][30], efficiently trapping QPs away from the JJ. Finally we conclude that such devices can be operated at high magnetic field without being limited by QPP, paving the way for implementing proposals for novel superconducting-topological hybrid qubits [31,32].…”

“…We attribute these to the orbital effect of the magnetic field, that occurs when the cylindrical electron density in the leads is threaded by magnetic flux, leading to the suppression of the proximity-induced gap [Fig. 4(d)] [26,27,30]. Such a cylindrical electron density profile is a manifestation of charge accumulation at the InAs NW surface for V g ≥ 0 [29].…”