Superconducting quantum dot and the sub-gap states

Abstract

Quantum dots are nanostructures made of semiconducting materials that are engineered to hold a small amount of electric charge (a few electrons) that is controlled by external gate and may hence be considered as tunable artificial atoms. A quantum dot may be contacted by conductive leads to become the active part of a single-electron transistor, a device that is highly conductive only at very specific gate voltages. In recent years a significant attention has been given to more complex hybrid devices, in particular superconductor-semiconductor heterostructures. Here I review the theoretical and experimental studies of small quantum-dot devices contacted by one or several superconducting leads. I focus on the research on the low-lying localized electronic excitations that exist inside the superconducting gap (Yu-Shiba-Rusinov states) and determine the transport properties of these devices. The sub-gap states can be accurately simulated using the numerical renormalization group technique, often providing full quantitative understanding of the observed phenomena.

13 pages, 4 figures

References in corpus (15)

• Signatures of Majorana fermions in hybrid superconductor-semiconductor nanowire devices
• Observation of Majorana Fermions in a Nb-InSb Nanowire-Nb Hybrid Quantum Device
• The numerical renormalization group method for quantum impurity systems
• Supercurrent reversal in quantum dots
• Sum-rule Conserving Spectral Functions from the Numerical Renormalization Group
• Energy resolution and discretization artefacts in the numerical renormalization group
• A Numerical Renormalization Group approach to Green's Functions for Quantum Impurity Models
• Josephson current through a single Anderson impurity coupled to BCS leads
• Even-odd effect in Andreev Transport through a Carbon Nanotube Quantum Dot
• Shiba states and zero-bias anomalies in the hybrid normal-superconductor Anderson model
• Tuning Yu-Shiba-Rusinov States in a Quantum Dot
• Magnetic anisotropy effects on quantum impurities in superconducting host
• Phase diagram and excitations of a Shiba molecule
• Coulomb blockade and Non-Fermi-liquid behavior in quantum dots
• Magnetic impurities in spin-split superconductors