Robustness of Yu-Shiba-Rusinov resonances in the presence of a complex superconducting order parameter

authored by: Jacob Senkpiel, Carmen Rubio-Verdú, Markus Etzkorn, Robert Drost, Leslie M. Schoop, Simon Dambach, Ciprian Padurariu, Björn Kubala, Joachim Ankerhold, Christian R. Ast, Klaus Kern
Abstract: Robust quantum systems rely on having a protective environment with minimized relaxation channels. Superconducting gaps play an important role in the design of such environments. The interaction of localized single spins with a conventional superconductor generally leads to intrinsically extremely narrow Yu-Shiba-Rusinov (YSR) resonances protected inside the superconducting gap. However, this may not apply to superconductors with more complex, energy-dependent order parameters. Exploiting the Fe-doped two-band superconductor NbSe2, we show that due to the nontrivial relation between its complex-valued and energy-dependent order parameters, YSR states are no longer restricted to be inside the gap. They can appear outside the gap (i.e., inside the coherence peaks), where they can also acquire a substantial intrinsic lifetime broadening. T-matrix scattering calculations show excellent agreement with the experimental data and relate the intrinsic YSR state broadening to the imaginary part of the host's order parameters. Our results suggest that nonthermal relaxation mechanisms contribute to the finite lifetime of the YSR states, even within the superconducting gap, making them less protected against residual interactions than previously assumed. YSR states may serve as valuable probes for nontrivial order parameters promoting a judicious selection of protective superconductors.
External Organisation(s): Max Planck Institute for Solid State Research (MPI-FKF)
CIC NanoGUNE Consolider
Princeton University
Ulm University
École polytechnique fédérale de Lausanne (EPFL)
Type: Article
Journal: Physical Review B
Volume: 100
ISSN: 2469-9950
Publication date: 01.07.2019
Publication status: Published
Peer reviewed: Yes
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Electronic version(s): https://doi.org/10.1103/physrevb.100.014502 (Access: Closed)

BibTeX

@article{3ad00fb59b104b4c820307510ebd2258,
title = "Robustness of Yu-Shiba-Rusinov resonances in the presence of a complex superconducting order parameter",
abstract = "Robust quantum systems rely on having a protective environment with minimized relaxation channels. Superconducting gaps play an important role in the design of such environments. The interaction of localized single spins with a conventional superconductor generally leads to intrinsically extremely narrow Yu-Shiba-Rusinov (YSR) resonances protected inside the superconducting gap. However, this may not apply to superconductors with more complex, energy-dependent order parameters. Exploiting the Fe-doped two-band superconductor NbSe2, we show that due to the nontrivial relation between its complex-valued and energy-dependent order parameters, YSR states are no longer restricted to be inside the gap. They can appear outside the gap (i.e., inside the coherence peaks), where they can also acquire a substantial intrinsic lifetime broadening. T-matrix scattering calculations show excellent agreement with the experimental data and relate the intrinsic YSR state broadening to the imaginary part of the host's order parameters. Our results suggest that nonthermal relaxation mechanisms contribute to the finite lifetime of the YSR states, even within the superconducting gap, making them less protected against residual interactions than previously assumed. YSR states may serve as valuable probes for nontrivial order parameters promoting a judicious selection of protective superconductors.",
author = "Jacob Senkpiel and Carmen Rubio-Verd{\'u} and Markus Etzkorn and Robert Drost and Schoop, {Leslie M.} and Simon Dambach and Ciprian Padurariu and Bj{\"o}rn Kubala and Joachim Ankerhold and Ast, {Christian R.} and Klaus Kern",
note = "Funding information: We gratefully acknowledge stimulating discussions with W. Belzig, H. Boschker, C. Cuevas, R. Kremer, B. Lotsch, J. Mannhart, F. Pauly, and M. Ternes. This work was funded in part by the ERC Consolidator Grant AbsoluteSpin (Grant No. 681164) and by the Center for Integrated Quantum Science and Technology ( IQ ST ). C.R.-V. acknowledges funding from the COST Action ECOST-STSM-CA15128-010217-082276. S.D. acknowledges financial support from the Carl-Zeiss-Stiftung.",
year = "2019",
month = jul,
day = "1",
doi = "10.1103/physrevb.100.014502",
language = "English",
volume = "100",
journal = "Physical Review B",
issn = "2469-9950",
publisher = "American Institute of Physics",
number = "1",
}