Yu–Shiba–Rusinov screening of spins in double quantum dots

A magnetic impurity coupled to a superconductor gives rise to a Yu–Shiba–Rusinov (YSR) state inside the superconducting energy gap. With increasing exchange coupling the excitation energy of this state eventually crosses zero and the system switches to a YSR ground state with bound quasiparticles sc...

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Bibliographic Details
Published in:Nature communications 2018-06, Vol.9 (1), p.2376-6, Article 2376
Main Authors: Grove-Rasmussen, K., Steffensen, G., Jellinggaard, A., Madsen, M. H., Žitko, R., Paaske, J., Nygård, J.
Format: Article
Language:English
Subjects:
639/766/119/1003
639/766/119/995
639/925/927/1007
639/925/927/1064
Arsenides
Conductance
Coupling
Energy gap
Gating
Honeycomb construction
Humanities and Social Sciences
Impurities
Indium
Indium arsenides
Mathematical models
multidisciplinary
Nanotechnology
Nanowires
Quantum dots
Resistance
Science
Science (multidisciplinary)
Screening
Switches
Topology
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Summary:A magnetic impurity coupled to a superconductor gives rise to a Yu–Shiba–Rusinov (YSR) state inside the superconducting energy gap. With increasing exchange coupling the excitation energy of this state eventually crosses zero and the system switches to a YSR ground state with bound quasiparticles screening the impurity spin by ħ /2. Here we explore indium arsenide (InAs) nanowire double quantum dots tunnel coupled to a superconductor and demonstrate YSR screening of spin-1/2 and spin-1 states. Gating the double dot through nine different charge states, we show that the honeycomb pattern of zero-bias conductance peaks, archetypal of double dots coupled to normal leads, is replaced by lines of zero-energy YSR states. These enclose regions of YSR-screened dot spins displaying distinctive spectral features, and their characteristic shape and topology change markedly with tunnel coupling strengths. We find excellent agreement with a simple zero-bandwidth approximation, and with numerical renormalization group calculations for the two-orbital Anderson model. Coupling superconductors to mesoscopic systems leads to unusual effects that could be exploited in new devices including topological quantum computers. Here the authors present a double quantum dot with a Yu–Shiba–Rusinov ground state arising from the interplay of Coulomb interactions and superconductivity.
ISSN:2041-1723
2041-1723
DOI:10.1038/s41467-018-04683-x