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Zero-Bias Anomaly in a Nanowire Quantum Dot Coupled to Superconductors

Eduardo J. H. Lee, Xiaocheng Jiang, Ramón Aguado, Georgios Katsaros, Charles M. Lieber, Silvano De Franceschi

DOI 10.1103/PhysRevLett.109.186802 · Physical Review Letters

T1

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Abstract

We studied the low-energy states of spin-1/2 quantum dots defined in InAs/InP nanowires and coupled to aluminum superconducting leads. By varying the superconducting gap Δ with a magnetic field B we investigated the transition from strong coupling Δ≪TK to weak-coupling Δ≫TK, where TK is the Kondo temperature. Below the critical field, we observe a persisting zero-bias Kondo resonance that vanishes only for low B or higher temperatures, leaving the room to more robust subgap structures at bias voltages between Δ and 2Δ. For strong and approximately symmetric tunnel couplings, a Josephson supercurrent is observed in addition to the Kondo peak. We ascribe the coexistence of a Kondo resonance and a superconducting gap to a significant density of intragap quasiparticle states, and the finite-bias subgap structures to tunneling through Shiba states. Our results, supported by numerical calculations, own relevance also in relation to tunnel-spectroscopy experiments aiming at the observation of Majorana fermions in hybrid nanostructures.

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FormulaReported Tc (K)Pressure (GPa)Type
Al

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1Pressure not reportedonset

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