Freiburg 2019 – wissenschaftliches Programm
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FM: Fall Meeting
FM 66: Poster: Entanglement
FM 66.7: Poster
Mittwoch, 25. September 2019, 16:30–18:30, Tents
Entanglement between Yu-Shiba-Rusinov states in STM devices — •Ciprian Padurariu1, Haonan Huang2, Simon Dambach1, Björn Kubala1, Christian Ast2, and Joachim Ankerhold1 — 1Institute for Complex Quantum Systems and IQST, Ulm University, 89069 Ulm, Germany — 2Max-Planck-Institut für Festkörperforschung, 70569 Stuttgart, Germany
We study the theory and experimental realization of tunneling between tip and substrate Shiba states in superconducting STM devices operating at 15 mK. We show that the elementary transport process involves splitting a Cooper pair, thereby entangling the spin of quasiparticles localized in the subgap states.
Our simple analytical results are in good agreement with conductance measurements exhibiting peaks in the tunnel current at a number of sub-gap bias voltages. [1] The voltages are identified as resonances of sub-gap discrete magnetic states, so called Shiba states, that form inside a volume around the magnetic impurity of coherence length size. [2]
The tunnel current between Shiba states gives rise to new resonances. These narrow current peaks are a result of the interplay between spin-entangled quasiparticle pairs and slow decoherence processes arising due to quasiparticle poisoning.
[1] M. Ruby, F. Pientka, Y. Peng, F. von Oppen, B. W. Heinrich, and K. J. Franke, Phys. Rev. Lett. 115, 087001 (2015).
[2] M. I. Salkola, A. V. Balatsky, and J. R. Schrieffer, Phys. Rev. B 55, 12648 (1997).