Spin-symmetric solution of an interacting quantum dot attached to superconducting leads: Andreev states and the $0-\pi$ transition
| Autor: | Janiš, V., Pokorný, V., Žonda, M. |
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| Rok vydání: | 2014 |
| Předmět: | |
| Zdroj: | Eur. Phys. J. B 89:197 (2016) |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1140/epjb/e2016-70299-7 |
| Popis: | Behavior of Andreev gap states in a quantum dot with Coulomb repulsion symmetrically attached to superconducting leads is studied via the perturbation expansion in the interaction strength. We find the exact asymptotic form of the spin-symmetric solution for the Andreev states continuously approaching the Fermi level. We thereby derive a critical interaction at which the Andreev states at zero temperature merge at the Fermi energy, being the upper bound for the $0-\pi$ transition. We show that the spin-symmetric solution becomes degenerate beyond this interaction, in the $\pi$ phase, and the Andreev states do not split unless the degeneracy is lifted. We further demonstrate that the degeneracy of the spin-symmetric state extends also into the $0$ phase in which the solutions with zero and non-zero frequencies of the Andreev states may coexist. Comment: 12 pages, 4 figures |
| Databáze: | arXiv |
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