Superconducting Proximity Effect in Quantum Dots

• Applicants: Professor Dr. Jürgen König; Dr. Stephan Weiß
• Subject Area: Theoretical Condensed Matter Physics
• Term: from 2011 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 193403257

• Final Report Year: 2019

Final Report Abstract

Well-defined and -controllable nanostructures such as quantum dots are ideal model systems to investigate the interplay of Coulomb interaction, nonequilibrium, and collective order. We study theoretically electronic transport through systems containing interacting quantum dots coupled to superconducting leads. Superconducting correlations are induced on the quantum dots by the equilibrium and nonequilibrium proximity effect and can be manipulated via gate and bias voltages. They affect the transport characteristics, e.g., of the Josephson or the local and the nonlocal Andreev currents. For hybrid systems involving noncollinear magnetism, unconventional superconducting pairing can be induced. Superconducting correlations can also be probed by analyzing the full counting statistics obtained by a time-resolved detection of individual electron-tunneling events. The main objective of the project was to develop and apply theoretical tools that properly take into account the important role played by Coulomb interaction in the quantum dot. On the one hand, we did this based on a diagrammatic real-time technique. On the other hand, we employed the numerically demanding ISPI scheme. We identified for various device geometries signatures of the induced conventional and unconventional superconducting correlations in transport quantities such as the current, the current noise, and higher-order factorial cumulants of the full counting statistics.

Publications

• Iterative path-integral summations for the tunneling magnetoresistance in interacting quantum-dot spin valves
  S. Mundinar, P. Stegmann, J. König, and S. Weiss
  
• Driven Superconducting Proximity Effect in Interacting Quantum Dots. Phys. Rev. B 85, 094518 (2012)
  A.G. Moghaddam, M. Governale, and J. König
  
• Iterative path integral summation for nonequilibrium quantum transport. Phys. Status Solidi B 250, 2298 (2013)
  S. Weiss, R. Hützen, D. Becker, J. Eckel, R. Egger, and M. Thorwart
  
• Josephson-Majorana Cycle in Topological Single-Electron Hybrid Transistors. Phys. Rev. B 88, 024512 (2013)
  N. Didier, M. Gibertini, A.G. Moghaddam, J. König, and R. Fazio
  
• Renormalization Effects in Interacting Quantum Dots Coupled to Superconducting Leads. Phys. Rev. B 87, 014509 (2013)
  D. Futterer, J. Swiebodzinski, M. Governale, and J. König
  
• Unconventional Superconductivity in Double Quantum Dots. Phys. Rev. B 90, 220501(R) (2014)
  B. Sothmann, S. Weiss, M. Governale, and J. König
  
• Detection of interactions via generalized factorial cumulants in systems in and out of equilibrium. Phys. Rev. B 92, 155413 (2015)
  P. Stegmann, B. Sothmann, A. Hucht, and J. König
  
• Odd-triplet superconductivity in single-level quantum dots. Phys. Rev. B 96, 064529 (2017)
  S. Weiss and J. König
  
• Coherent dynamics in stochastic systems revealed by full counting statistics. Phys. Rev. B 98, 035409 (2018)
  P. Stegmann, J. König, and S. Weiss
  
• Revealing attractive electron-electron interaction in quantum dots by full counting statistics. New J. Phys. 20, 073023 (2018)
  E. Kleinherbers, P. Stegmann, and J. König