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Yu-Shiba-Rusinov states in phase-biased superconductor-quantum dot-superconductor junctions

Kirsanskas, Gediminas LU ; Goldstein, Moshe; Flensberg, Karsten; Glazman, Leonid I. and Paaske, Jens (2015) In Physical Review B (Condensed Matter and Materials Physics) 92(23).
Abstract
We study the effects of a phase difference on Yu-Shiba-Rusinov (YSR) states in a spinful Coulomb-blockaded quantum dot contacted by a superconducting loop. In the limit where charging energy is larger than the superconducting gap, we determine the subgap excitation spectrum, the corresponding supercurrent, and the differential conductance as measured by a normal-metal tunnel probe. In absence of a phase difference only one linear combination of the superconductor lead electrons couples to the spin, which gives a single YSR state. With finite phase difference, however, it is effectively a two-channel scattering problem and therefore an additional state emerges from the gap edge. The energy of the phase-dependent YSR states depend on the... (More)
We study the effects of a phase difference on Yu-Shiba-Rusinov (YSR) states in a spinful Coulomb-blockaded quantum dot contacted by a superconducting loop. In the limit where charging energy is larger than the superconducting gap, we determine the subgap excitation spectrum, the corresponding supercurrent, and the differential conductance as measured by a normal-metal tunnel probe. In absence of a phase difference only one linear combination of the superconductor lead electrons couples to the spin, which gives a single YSR state. With finite phase difference, however, it is effectively a two-channel scattering problem and therefore an additional state emerges from the gap edge. The energy of the phase-dependent YSR states depend on the gate voltage and one state can cross zero energy twice inside the valley with odd occupancy. These crossings are shifted by the phase difference towards the charge degeneracy points, corresponding to larger exchange couplings. Moreover, the zero-energy crossings give rise to resonant peaks in the differential conductance with magnitude 4e(2)/h. Finally, we demonstrate that the quantum fluctuations of the dot spin do not alter qualitatively any of the results. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Physical Review B (Condensed Matter and Materials Physics)
volume
92
issue
23
publisher
American Physical Society
external identifiers
  • wos:000366493300006
  • scopus:84950335624
ISSN
1098-0121
DOI
10.1103/PhysRevB.92.235422
language
English
LU publication?
yes
id
63050f16-00f0-4299-a419-c2be6963a2d2 (old id 8556937)
date added to LUP
2016-01-26 13:54:18
date last changed
2017-08-13 04:03:06
@article{63050f16-00f0-4299-a419-c2be6963a2d2,
  abstract     = {We study the effects of a phase difference on Yu-Shiba-Rusinov (YSR) states in a spinful Coulomb-blockaded quantum dot contacted by a superconducting loop. In the limit where charging energy is larger than the superconducting gap, we determine the subgap excitation spectrum, the corresponding supercurrent, and the differential conductance as measured by a normal-metal tunnel probe. In absence of a phase difference only one linear combination of the superconductor lead electrons couples to the spin, which gives a single YSR state. With finite phase difference, however, it is effectively a two-channel scattering problem and therefore an additional state emerges from the gap edge. The energy of the phase-dependent YSR states depend on the gate voltage and one state can cross zero energy twice inside the valley with odd occupancy. These crossings are shifted by the phase difference towards the charge degeneracy points, corresponding to larger exchange couplings. Moreover, the zero-energy crossings give rise to resonant peaks in the differential conductance with magnitude 4e(2)/h. Finally, we demonstrate that the quantum fluctuations of the dot spin do not alter qualitatively any of the results.},
  articleno    = {235422},
  author       = {Kirsanskas, Gediminas and Goldstein, Moshe and Flensberg, Karsten and Glazman, Leonid I. and Paaske, Jens},
  issn         = {1098-0121},
  language     = {eng},
  number       = {23},
  publisher    = {American Physical Society},
  series       = {Physical Review B (Condensed Matter and Materials Physics)},
  title        = {Yu-Shiba-Rusinov states in phase-biased superconductor-quantum dot-superconductor junctions},
  url          = {http://dx.doi.org/10.1103/PhysRevB.92.235422},
  volume       = {92},
  year         = {2015},
}